JavaScript 进阶问题列表

我在我的 Instagram](https://www.instagram.com/theavocoder)) 上每天都会发布 JavaScript 的多选问题，并且同时也会在这个仓库中发布。

从基础到进阶，测试你有多了解 JavaScript，刷新你的知识，或者帮助你的 coding 面试！
:muscle: :rocket: 我每周都会在这个仓库下更新新的问题。

答案在问题下方的折叠部分，点击即可展开问题。祝你好运 :heart:

1. 输出是什么？

function sayHi() {
  console.log(name)
  console.log(age)
  var name = 'Lydia'
  let age = 21
}
sayHi()

• A: Lydia 和 undefined
• B: Lydia 和 ReferenceError
• C: ReferenceError 和 21
• D: undefined 和 ReferenceError

2. 输出是什么？

```javascript
for (var i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 1)
}

for (let i = 0; i < 3; i++) {
setTimeout(() => console.log(i), 1)
}
```

• A: 0 1 2 和 0 1 2
  - B: 0 1 2 和 3 3 3
  - C: 3 3 3 和 0 1 2

3. 输出是什么？

```javascript
const shape = {
radius: 10,
diameter() {
return this.radius 2
},
perimeter: () => 2 Math.PI * this.radius
}

shape.diameter()
shape.perimeter()
```

• A: 20 and 62.83185307179586
  - B: 20 and NaN
  - C: 20 and 63
  - D: NaN and 63

4. 输出是什么？

javascript<br />+true;<br />!"Lydia";<br />

• A: 1 and false
  - B: false and NaN
  - C: false and false

5. 哪一个是正确的？

```javascript
const bird = {
size: ‘small’
}

const mouse = {
name: ‘Mickey’,
small: true
}
```

• A: mouse.bird.size是无效的
  - B: mouse[bird.size]是无效的
  - C: mouse[bird["size"]]是无效的
  - D: 以上三个选项都是有效的

6. 输出是什么？

```javascript
let c = { greeting: ‘Hey!’ }
let d

d = c
c.greeting = ‘Hello’
console.log(d.greeting)
```

• A: Hello
  - B: undefined
  - C: ReferenceError
  - D: TypeError

7. 输出是什么？

```javascript
let a = 3
let b = new Number(3)
let c = 3

console.log(a == b)
console.log(a === b)
console.log(b === c)
```

• A: true false true
  - B: false false true
  - C: true false false
  - D: false true true

8. 输出是什么？

```javascript
class Chameleon {
static colorChange(newColor) {
this.newColor = newColor
return this.newColor
}

constructor({ newColor = ‘green’ } = {}) {
this.newColor = newColor
}
}

const freddie = new Chameleon({ newColor: ‘purple’ })
freddie.colorChange(‘orange’)
```

• A: orange
  - B: purple
  - C: green
  - D: TypeError

9. 输出是什么？

javascript<br />let greeting<br />greetign = {} // Typo!<br />console.log(greetign)<br />

• A: {}
  - B: ReferenceError: greetign is not defined
  - C: undefined

10. 当我们这么做时，会发生什么？

```javascript
function bark() {
console.log(‘Woof!’)
}

bark.animal = ‘dog’
```

• A: 正常运行!
  - B: SyntaxError. 你不能通过这种方式给函数增加属性。
  - C: undefined
  - D: ReferenceError

11. 输出是什么？

```javascript
function Person(firstName, lastName) {
this.firstName = firstName;
this.lastName = lastName;
}

const member = new Person(“Lydia”, “Hallie”);
Person.getFullName = function () {
return ${this.firstName} ${this.lastName};
}

console.log(member.getFullName());
```

• A: TypeError
  - B: SyntaxError
  - C: Lydia Hallie
  - D: undefined undefined

12. 输出是什么？

```javascript
function Person(firstName, lastName) {
this.firstName = firstName
this.lastName = lastName
}

const lydia = new Person(‘Lydia’, ‘Hallie’)
const sarah = Person(‘Sarah’, ‘Smith’)

console.log(lydia)
console.log(sarah)
```

• A: Person {firstName: "Lydia", lastName: "Hallie"} and undefined
  - B: Person {firstName: "Lydia", lastName: "Hallie"} and Person {firstName: "Sarah", lastName: "Smith"}
  - C: Person {firstName: "Lydia", lastName: "Hallie"} and {}
  - D:Person {firstName: "Lydia", lastName: "Hallie"} and ReferenceError

13. 事件传播的三个阶段是什么？

• A: Target > Capturing > Bubbling
  - B: Bubbling > Target > Capturing
  - C: Target > Bubbling > Capturing
  - D: Capturing > Target > Bubbling

14. 所有对象都有原型。

• A: 对
  - B: 错

15. 输出是什么？

```javascript
function sum(a, b) {
return a + b
}

sum(1, ‘2’)
```

• A: NaN
  - B: TypeError
  - C: "12"
  - D: 3

16. 输出是什么？

javascript<br />let number = 0<br />console.log(number++)<br />console.log(++number)<br />console.log(number)<br />

• A: 1 1 2
  - B: 1 2 2
  - C: 0 2 2
  - D: 0 1 2

17. 输出是什么？

```javascript
function getPersonInfo(one, two, three) {
console.log(one)
console.log(two)
console.log(three)
}

const person = ‘Lydia’
const age = 21

getPersonInfo${person} is ${age} years old
```

• A: "Lydia" 21 ["", " is ", " years old"]
  - B: ["", " is ", " years old"] "Lydia" 21
  - C: "Lydia" ["", " is ", " years old"] 21

18. 输出是什么？

``javascript<br />function checkAge(data) {<br /> if (data === { age: 18 }) {<br /> console.log('You are an adult!')<br /> } else if (data == { age: 18 }) {<br /> console.log('You are still an adult.')<br /> } else {<br /> console.log(Hmm.. You don’t have an age I guess`)
}
}

checkAge({ age: 18 })
```

• A: You are an adult!
  - B: You are still an adult.
  - C: Hmm.. You don't have an age I guess

19. 输出是什么？

```javascript
function getAge(…args) {
console.log(typeof args)
}

getAge(21)
```

• A: "number"
  - B: "array"
  - C: "object"
  - D: "NaN"

20. 输出是什么？

```javascript
function getAge() {
‘use strict’
age = 21
console.log(age)
}

getAge()
```

• A: 21
  - B: undefined
  - C: ReferenceError
  - D: TypeError

21. 输出是什么？

javascript<br />const sum = eval('10*10+5')<br />

• A: 105
  - B: "105"
  - C: TypeError
  - D: "10*10+5"

22. cool_secret 可访问多长时间？

javascript<br />sessionStorage.setItem('cool_secret', 123)<br />

• A: 永远，数据不会丢失。
  - B: 当用户关掉标签页时。
  - C: 当用户关掉整个浏览器，而不只是关掉标签页。
  - D: 当用户关闭电脑时。

23. 输出是什么？

```javascript
var num = 8
var num = 10

console.log(num)
```

• A: 8
  - B: 10
  - C: SyntaxError
  - D: ReferenceError

24. 输出是什么？

```javascript
const obj = { 1: ‘a’, 2: ‘b’, 3: ‘c’ }
const set = new Set([1, 2, 3, 4, 5])

obj.hasOwnProperty(‘1’)
obj.hasOwnProperty(1)
set.has(‘1’)
set.has(1)
```

• A: false true false true
  - B: false true true true
  - C: true true false true
  - D: true true true true

25. 输出是什么？

javascript<br />const obj = { a: 'one', b: 'two', a: 'three' }<br />console.log(obj)<br />

• A: { a: "one", b: "two" }
  - B: { b: "two", a: "three" }
  - C: { a: "three", b: "two" }
  - D: SyntaxError

26. JavaScript 全局执行上下文为你做了两件事：全局对象和 this 关键字。

• A: 对
  - B: 错
  - C: 看情况

27. 输出是什么？

javascript<br />for (let i = 1; i < 5; i++) {<br /> if (i === 3) continue<br /> console.log(i)<br />}<br />

• A: 1 2
  - B: 1 2 3
  - C: 1 2 4
  - D: 1 3 4

28. 输出是什么？

```javascript
String.prototype.giveLydiaPizza = () => {
return ‘Just give Lydia pizza already!’
}

const name = ‘Lydia’

name.giveLydiaPizza()
```

• A: "Just give Lydia pizza already!"
  - B: TypeError: not a function
  - C: SyntaxError
  - D: undefined

29. 输出是什么？

```javascript
const a = {}
const b = { key: ‘b’ }
const c = { key: ‘c’ }

a[b] = 123
a[c] = 456

console.log(a[b])
```

• A: 123
  - B: 456
  - C: undefined
  - D: ReferenceError

30. 输出是什么？

```javascript
const foo = () => console.log(‘First’)
const bar = () => setTimeout(() => console.log(‘Second’))
const baz = () => console.log(‘Third’)

bar()
foo()
baz()
```

• A: First Second Third
  - B: First Third Second
  - C: Second First Third
  - D: Second Third First

31. 当点击按钮时，event.target是什么？

html<br /><div onclick="console.log('first div')"><br /> <div onclick="console.log('second div')"><br /> <button onclick="console.log('button')"><br /> Click!<br /> </button><br /> </div><br /></div><br />

• A: Outer div
  - B: Inner div
  - C: button
  - D: 一个包含所有嵌套元素的数组。

32. 当您单击该段落时，日志输出是什么？

html<br /><div onclick="console.log('div')"><br /> <p onclick="console.log('p')"><br /> Click here!<br /> </p><br /></div><br />

• A: p div
  - B: div p
  - C: p
  - D: div

33. 输出是什么？

```javascript
const person = { name: ‘Lydia’ }

function sayHi(age) {
console.log(${this.name} is ${age})
}

sayHi.call(person, 21)
sayHi.bind(person, 21)
```

• A: undefined is 21 Lydia is 21
  - B: function function
  - C: Lydia is 21 Lydia is 21
  - D: Lydia is 21 function

34. 输出是什么？

```javascript
function sayHi() {
return (() => 0)()
}

typeof sayHi()
```

• A: "object"
  - B: "number"
  - C: "function"
  - D: "undefined"

35. 下面哪些值是 falsy?

javascript<br />0<br />new Number(0)<br />('')<br />(' ')<br />new Boolean(false)<br />undefined<br />

• A: 0, '', undefined
  - B: 0, new Number(0), '', new Boolean(false), undefined
  - C: 0, '', new Boolean(false), undefined
  - D: All of them are falsy

36. 输出是什么？

javascript<br />console.log(typeof typeof 1)<br />

• A: "number"
  - B: "string"
  - C: "object"
  - D: "undefined"

37. 输出是什么？

javascript<br />const numbers = [1, 2, 3]<br />numbers[10] = 11<br />console.log(numbers)<br />

• A: [1, 2, 3, 7 x null, 11]
  - B: [1, 2, 3, 11]
  - C: [1, 2, 3, 7 x empty, 11]
  - D: SyntaxError

38. 输出是什么？

javascript<br />(() => {<br /> let x, y<br /> try {<br /> throw new Error()<br /> } catch (x) {<br /> (x = 1), (y = 2)<br /> console.log(x)<br /> }<br /> console.log(x)<br /> console.log(y)<br />})()<br />

• A: 1 undefined 2
  - B: undefined undefined undefined
  - C: 1 1 2
  - D: 1 undefined undefined

39. JavaScript 中的一切都是？

• A: 基本类型与对象
  - B: 函数与对象
  - C: 只有对象
  - D: 数字与对象
  -
  
  答案

  
  

答案: A

JavaScript 只有基本类型和对象。

基本类型包括 boolean, null, undefined, bigint, number, string, symbol。

40. 输出是什么？

javascript<br />[[0, 1], [2, 3]].reduce(<br /> (acc, cur) => {<br /> return acc.concat(cur)<br /> },<br /> [1, 2]<br />)<br />

• A: [0, 1, 2, 3, 1, 2]
  - B: [6, 1, 2]
  - C: [1, 2, 0, 1, 2, 3]
  - D: [1, 2, 6]

41. 输出是什么？

javascript<br />!!null<br />!!''<br />!!1<br />

• A: false true false
  - B: false false true
  - C: false true true
  - D: true true false

42. setInterval 方法的返回值是什么？

javascript<br />setInterval(() => console.log('Hi'), 1000)<br />

• A: 一个唯一的id
  - B: 该方法指定的毫秒数
  - C: 传递的函数
  - D: undefined

43. 输出是什么？

javascript<br />[...'Lydia']<br />

• A: ["L", "y", "d", "i", "a"]
  - B: ["Lydia"]
  - C: [[], "Lydia"]
  - D: [["L", "y", "d", "i", "a"]]

44. 输出是什么?

```javascript
function generator(i) {
yield i;
yield i 2;
}

const gen = generator(10);

console.log(gen.next().value);
console.log(gen.next().value);
```

• A: [0, 10], [10, 20]
  - B: 20, 20
  - C: 10, 20
  - D: 0, 10 and 10, 20

45. 返回值是什么?

```javascript
const firstPromise = new Promise((res, rej) => {
setTimeout(res, 500, “one”);
});

const secondPromise = new Promise((res, rej) => {
setTimeout(res, 100, “two”);
});

Promise.race([firstPromise, secondPromise]).then(res => console.log(res));
```

• A: "one"
  - B: "two"
  - C: "two" "one"
  - D: "one" "two"

46. 输出是什么?

```javascript
let person = { name: “Lydia” };
const members = [person];
person = null;

console.log(members);
```

• A: null
  - B: [null]
  - C: [{}]
  - D: [{ name: "Lydia" }]

47. 输出是什么?

```javascript
const person = {
name: “Lydia”,
age: 21
};

for (const item in person) {
console.log(item);
}
```

• A: { name: "Lydia" }, { age: 21 }
  - B: "name", "age"
  - C: "Lydia", 21
  - D: ["name", "Lydia"], ["age", 21]

48. 输出是什么?

javascript<br />console.log(3 + 4 + "5");<br />

• A: "345"
  - B: "75"
  - C: 12
  - D: "12"

49. num的值是什么?

javascript<br />const num = parseInt("7*6", 10);<br />

• A: 42
  - B: "42"
  - C: 7
  - D: NaN

50. 输出是什么?

javascript<br />[1, 2, 3].map(num => {<br /> if (typeof num === "number") return;<br /> return num * 2;<br />});<br />

• A: []
  - B: [null, null, null]
  - C: [undefined, undefined, undefined]
  - D: [ 3 x empty ]

51. 输出的是什么?

```javascript
function getInfo(member, year) {
member.name = “Lydia”;
year = “1998”;
}

const person = { name: “Sarah” };
const birthYear = “1997”;

getInfo(person, birthYear);

console.log(person, birthYear);
```

• A: { name: "Lydia" }, "1997"
  - B: { name: "Sarah" }, "1998"
  - C: { name: "Lydia" }, "1998"
  - D: { name: "Sarah" }, "1997"

52. 输出是什么?

```javascript
function greeting() {
throw “Hello world!”;
}

function sayHi() {
try {
const data = greeting();
console.log(“It worked!”, data);
} catch (e) {
console.log(“Oh no an error:”, e);
}
}

sayHi();
```

• A: "It worked! Hello world!"
  - B: "Oh no an error: undefined
  - C: SyntaxError: can only throw Error objects
  - D: "Oh no an error: Hello world!

53. 输出是什么?

```javascript
function Car() {
this.make = “Lamborghini”;
return { make: “Maserati” };
}

const myCar = new Car();
console.log(myCar.make);
```

• A: "Lamborghini"
  - B: "Maserati"
  - C: ReferenceError
  - D: TypeError

54. 输出是什么?

```javascript
(() => {
let x = (y = 10);
})();

console.log(typeof x);
console.log(typeof y);
```

• A: "undefined", "number"
  - B: "number", "number"
  - C: "object", "number"
  - D: "number", "undefined"

55. 输出是什么?

```javascript
class Dog {
constructor(name) {
this.name = name;
}
}

Dog.prototype.bark = function() {
console.log(Woof I am ${this.name});
};

const pet = new Dog(“Mara”);

pet.bark();

delete Dog.prototype.bark;

pet.bark();
```

• A: "Woof I am Mara", TypeError
  - B: "Woof I am Mara","Woof I am Mara"
  - C: "Woof I am Mara", undefined
  - D: TypeError, TypeError

56. 输出是什么?

```javascript
const set = new Set([1, 1, 2, 3, 4]);

console.log(set);
```

• A: [1, 1, 2, 3, 4]
  - B: [1, 2, 3, 4]
  - C: {1, 1, 2, 3, 4}
  - D: {1, 2, 3, 4}

57. 输出是什么?

javascript<br />// counter.js<br />let counter = 10;<br />export default counter;<br />

```javascript
// index.js
import myCounter from “./counter”;

myCounter += 1;

console.log(myCounter);
```

• A: 10
  - B: 11
  - C: Error
  - D: NaN

58. 输出是什么?

```javascript
const name = “Lydia”;
age = 21;

console.log(delete name);
console.log(delete age);
```

• A: false, true
  - B: "Lydia", 21
  - C: true, true
  - D: undefined, undefined

59. 输出是什么?

```javascript
const numbers = [1, 2, 3, 4, 5];
const [y] = numbers;

console.log(y);
```

• A: [[1, 2, 3, 4, 5]]
  - B: [1, 2, 3, 4, 5]
  - C: 1
  - D: [1]

60. 输出是什么?

```javascript
const user = { name: “Lydia”, age: 21 };
const admin = { admin: true, …user };

console.log(admin);
```

• A: { admin: true, user: { name: "Lydia", age: 21 } }
  - B: { admin: true, name: "Lydia", age: 21 }
  - C: { admin: true, user: ["Lydia", 21] }
  - D: { admin: true }

61. 输出是什么?

```javascript
const person = { name: “Lydia” };

Object.defineProperty(person, “age”, { value: 21 });

console.log(person);
console.log(Object.keys(person));
```

• A: { name: "Lydia", age: 21 }, ["name", "age"]
  - B: { name: "Lydia", age: 21 }, ["name"]
  - C: { name: "Lydia"}, ["name", "age"]
  - D: { name: "Lydia"}, ["age"]

62. 输出是什么?

```javascript
const settings = {
username: “lydiahallie”,
level: 19,
health: 90
};

const data = JSON.stringify(settings, [“level”, “health”]);
console.log(data);
```

• A: "{"level":19, "health":90}"
  - B: "{"username": "lydiahallie"}"
  - C: "["level", "health"]"
  - D: "{"username": "lydiahallie", "level":19, "health":90}"

63. 输出是什么?

```javascript
let num = 10;

const increaseNumber = () => num++;
const increasePassedNumber = number => number++;

const num1 = increaseNumber();
const num2 = increasePassedNumber(num1);

console.log(num1);
console.log(num2);
```

• A: 10, 10
  - B: 10, 11
  - C: 11, 11
  - D: 11, 12

64. 输出什么?

```javascript
const value = { number: 10 };

const multiply = (x = { …value }) => {
console.log(x.number *= 2);
};

multiply();
multiply();
multiply(value);
multiply(value);
```

• A: 20, 40, 80, 160
  - B: 20, 40, 20, 40
  - C: 20, 20, 20, 40
  - D: NaN, NaN, 20, 40

65. 输出什么?

javascript<br />[1, 2, 3, 4].reduce((x, y) => console.log(x, y));<br />

• A: 1 2 and 3 3 and 6 4
  - B: 1 2 and 2 3 and 3 4
  - C: 1 undefined and 2 undefined and 3 undefined and 4 undefined
  - D: 1 2 and undefined 3 and undefined 4

66. 使用哪个构造函数可以成功继承Dog类?

```javascript
class Dog {
constructor(name) {
this.name = name;
}
};

class Labrador extends Dog {
// 1
constructor(name, size) {
this.size = size;
}
// 2
constructor(name, size) {
super(name);
this.size = size;
}
// 3
constructor(size) {
super(name);
this.size = size;
}
// 4
constructor(name, size) {
this.name = name;
this.size = size;
}

};
```

• A: 1
  - B: 2
  - C: 3
  - D: 4

67. 输出什么?

```javascript
// index.js
console.log(‘running index.js’);
import { sum } from ‘./sum.js’;
console.log(sum(1, 2));

// sum.js
console.log(‘running sum.js’);
export const sum = (a, b) => a + b;
```

• A: running index.js, running sum.js, 3
  - B: running sum.js, running index.js, 3
  - C: running sum.js, 3, running index.js
  - D: running index.js, undefined, running sum.js

68. 输出什么?

javascript<br />console.log(Number(2) === Number(2))<br />console.log(Boolean(false) === Boolean(false))<br />console.log(Symbol('foo') === Symbol('foo'))<br />

• A: true, true, false
  - B: false, true, false
  - C: true, false, true
  - D: true, true, true

69. 输出什么?

javascript<br />const name = "Lydia Hallie"<br />console.log(name.padStart(13))<br />console.log(name.padStart(2))<br />

• A: "Lydia Hallie", "Lydia Hallie"
  - B: " Lydia Hallie", " Lydia Hallie" ("[13x whitespace]Lydia Hallie", "[2x whitespace]Lydia Hallie")
  - C: " Lydia Hallie", "Lydia Hallie" ("[1x whitespace]Lydia Hallie", "Lydia Hallie")
  - D: "Lydia Hallie", "Lyd"

70. 输出什么?

javascript<br />console.log("🥑" + "💻");<br />

• A: "🥑💻"
  - B: 257548
  - C: A string containing their code points
  - D: Error

71. 如何能打印出console.log语句后注释掉的值？

```javascript
function* startGame() {
const 答案 = yield “Do you love JavaScript?”;
if (答案 !== “Yes”) {
return “Oh wow… Guess we’re gone here”;
}
return “JavaScript loves you back ❤️”;
}

const game = startGame();
console.log(/ 1 /); // Do you love JavaScript?
console.log(/ 2 /); // JavaScript loves you back ❤️
```

• A: game.next("Yes").value and game.next().value
  - B: game.next.value("Yes") and game.next.value()
  - C: game.next().value and game.next("Yes").value
  - D: game.next.value() and game.next.value("Yes")

72. 输出什么?

javascript<br />console.log(String.raw`Hello\nworld`);<br />

• A: Hello world!
  - B: Hello
     world
  - C: Hello\nworld
  - D: Hello\n
     world

73. 输出什么?

```javascript
async function getData() {
return await Promise.resolve(“I made it!”);
}

const data = getData();
console.log(data);
```

• A: "I made it!"
  - B: Promise {<resolved>: "I made it!"}
  - C: Promise {<pending>}
  - D: undefined

74. 输出什么?

```javascript
function addToList(item, list) {
return list.push(item);
}

const result = addToList(“apple”, [“banana”]);
console.log(result);
```

• A: ['apple', 'banana']
  - B: 2
  - C: true
  - D: undefined

75. 输出什么?

```javascript
const box = { x: 10, y: 20 };

Object.freeze(box);

const shape = box;
shape.x = 100;
console.log(shape)
```

• A: { x: 100, y: 20 }
  - B: { x: 10, y: 20 }
  - C: { x: 100 }
  - D: ReferenceError

76. 输出什么?

```javascript
const { name: myName } = { name: “Lydia” };

console.log(name);
```

• A: "Lydia"
  - B: "myName"
  - C: undefined
  - D: ReferenceError

77. 以下是个纯函数么?

javascript<br />function sum(a, b) {<br /> return a + b;<br />}<br />

• A: Yes
  - B: No

78. 输出什么?

``javascript<br />const add = () => {<br /> const cache = {};<br /> return num => {<br /> if (num in cache) {<br /> returnFrom cache! ${cache[num]};<br /> } else {<br /> const result = num + 10;<br /> cache[num] = result;<br /> returnCalculated! ${result}`;
}
};
};

const addFunction = add();
console.log(addFunction(10));
console.log(addFunction(10));
console.log(addFunction(5 * 2));
```

• A: Calculated! 20 Calculated! 20 Calculated! 20
  - B: Calculated! 20 From cache! 20 Calculated! 20
  - C: Calculated! 20 From cache! 20 From cache! 20
  - D: Calculated! 20 From cache! 20 Error

79. 输出什么?

```javascript
const myLifeSummedUp = [“☕”, “💻”, “🍷”, “🍫”]

for (let item in myLifeSummedUp) {
console.log(item)
}

for (let item of myLifeSummedUp) {
console.log(item)
}
```

• A: 0 1 2 3 and "☕" "💻" "🍷" "🍫"
  - B: "☕" "💻" "🍷" "🍫" and "☕" "💻" "🍷" "🍫"
  - C: "☕" "💻" "🍷" "🍫" and 0 1 2 3
  - D: 0 1 2 3 and {0: "☕", 1: "💻", 2: "🍷", 3: "🍫"}

80. 输出什么?

javascript<br />const list = [1 + 2, 1 * 2, 1 / 2]<br />console.log(list)<br />

• A: ["1 + 2", "1 * 2", "1 / 2"]
  - B: ["12", 2, 0.5]
  - C: [3, 2, 0.5]
  - D: [1, 1, 1]

81. 输出什么?

``javascript<br />function sayHi(name) {<br /> returnHi there, ${name}`
}

console.log(sayHi())
```

• A: Hi there,
  - B: Hi there, undefined
  - C: Hi there, null
  - D: ReferenceError

82. 输出什么?

```javascript
var status = “😎”

setTimeout(() => {
const status = “😍”

const data = {
status: “🥑”,
getStatus() {
return this.status
}
}

console.log(data.getStatus())
console.log(data.getStatus.call(this))
}, 0)
```

• A: "🥑" and "😍"
  - B: "🥑" and "😎"
  - C: "😍" and "😎"
  - D: "😎" and "😎"

83. 输出什么?

```javascript
const person = {
name: “Lydia”,
age: 21
}

let city = person.city
city = “Amsterdam”

console.log(person)
```

• A: { name: "Lydia", age: 21 }
  - B: { name: "Lydia", age: 21, city: "Amsterdam" }
  - C: { name: "Lydia", age: 21, city: undefined }
  - D: "Amsterdam"

84. 输出什么?

```javascript
function checkAge(age) {
if (age < 18) {
const message = “Sorry, you’re too young.”
} else {
const message = “Yay! You’re old enough!”
}

return message
}

console.log(checkAge(21))
```

• A: "Sorry, you're too young."
  - B: "Yay! You're old enough!"
  - C: ReferenceError
  - D: undefined

85. 什么样的信息将被打印?

javascript<br />fetch('[https://www.website.com/api/user/1')](https://www.website.com/api/user/1'))<br /> .then(res => res.json())<br /> .then(res => console.log(res))<br />

• A: fetch方法的结果
  - B: 第二次调用fetch方法的结果
  - C: 前一个.then()中回调方法返回的结果
  - D: 总是undefined

86. 哪个选项是将hasName设置为true的方法，前提是不能将true作为参数传递?

javascript<br />function getName(name) {<br /> const hasName = //<br />}<br />

• A: !!name
  - B: name
  - C: new Boolean(name)
  - D: name.length

87. 输出什么?

javascript<br />console.log("I want pizza"[0])<br />

• A: """
  - B: "I"
  - C: SyntaxError
  - D: undefined

88. 输出什么?

```javascript
function sum(num1, num2 = num1) {
console.log(num1 + num2)
}

sum(10)
```

• A: NaN
  - B: 20
  - C: ReferenceError
  - D: undefined

89. 输出什么?

```javascript
// module.js
export default () => “Hello world”
export const name = “Lydia”

// index.js
import * as data from “./module”

console.log(data)
```

• A: { default: function default(), name: "Lydia" }
  - B: { default: function default() }
  - C: { default: "Hello world", name: "Lydia" }
  - D: Global object of module.js

90. 输出什么?

```javascript
class Person {
constructor(name) {
this.name = name
}
}

const member = new Person(“John”)
console.log(typeof member)
```

• A: "class"
  - B: "function"
  - C: "object"
  - D: "string"

91. 输出什么?

```javascript
let newList = [1, 2, 3].push(4)

console.log(newList.push(5))
```

• A: [1, 2, 3, 4, 5]
  - B: [1, 2, 3, 5]
  - C: [1, 2, 3, 4]
  - D: Error

92. 输出什么?

```javascript
function giveLydiaPizza() {
return “Here is pizza!”
}

const giveLydiaChocolate = () => “Here’s chocolate… now go hit the gym already.”

console.log(giveLydiaPizza.prototype)
console.log(giveLydiaChocolate.prototype)
```

• A: { constructor: ...} { constructor: ...}
  - B: {} { constructor: ...}
  - C: { constructor: ...} {}
  - D: { constructor: ...} undefined

93. 输出什么?

```javascript
const person = {
name: “Lydia”,
age: 21
}

for (const [x, y] of Object.entries(person)) {
console.log(x, y)
}
```

• A: name Lydia and age 21
  - B: ["name", "Lydia"] and ["age", 21]
  - C: ["name", "age"] and undefined
  - D: Error

94. 输出什么?

```javascript
function getItems(fruitList, …args, favoriteFruit) {
return […fruitList, …args, favoriteFruit]
}

getItems([“banana”, “apple”], “pear”, “orange”)
```

• A: ["banana", "apple", "pear", "orange"]
  - B: [["banana", "apple"], "pear", "orange"]
  - C: ["banana", "apple", ["pear"], "orange"]
  - D: SyntaxError

95. 输出什么?

```javascript
function nums(a, b) {
if
(a > b)
console.log(‘a is bigger’)
else
console.log(‘b is bigger’)
return
a + b
}

console.log(nums(4, 2))
console.log(nums(1, 2))
```

• A: a is bigger, 6 and b is bigger, 3
  - B: a is bigger, undefined and b is bigger, undefined
  - C: undefined and undefined
  - D: SyntaxError

96. 输出什么?

```javascript
class Person {
constructor() {
this.name = “Lydia”
}
}

Person = class AnotherPerson {
constructor() {
this.name = “Sarah”
}
}

const member = new Person()
console.log(member.name)
```

• A: "Lydia"
  - B: "Sarah"
  - C: Error: cannot redeclare Person
  - D: SyntaxError

97. 输出什么?

```javascript
const info = {
[Symbol(‘a’)]: ‘b’
}

console.log(info)
console.log(Object.keys(info))
```

• A: {Symbol('a'): 'b'} and ["{Symbol('a')"]
  - B: {} and []
  - C: { a: "b" } and ["a"]
  - D: {Symbol('a'): 'b'} and []

98. 输出什么?

```javascript
const getList = ([x, …y]) => [x, y]
const getUser = user => { name: user.name, age: user.age }

const list = [1, 2, 3, 4]
const user = { name: “Lydia”, age: 21 }

console.log(getList(list))
console.log(getUser(user))
```

• A: [1, [2, 3, 4]] and SyntaxError
  - B: [1, [2, 3, 4]] and { name: "Lydia", age: 21 }
  - C: [1, 2, 3, 4] and { name: "Lydia", age: 21 }
  - D: Error and { name: "Lydia", age: 21 }

99. 输出什么?

```javascript
const name = “Lydia”

console.log(name())
```

• A: SyntaxError
  - B: ReferenceError
  - C: TypeError
  - D: undefined

100. 输出什么?

```javascript
// 🎉✨ This is my 100th question! ✨🎉

const output = ${[] && 'Im'}possible!<br />You should${'' &&n’t} see a therapist after so much JavaScript lol
```

• A: possible! You should see a therapist after so much JavaScript lol
  - B: Impossible! You should see a therapist after so much JavaScript lol
  - C: possible! You shouldn't see a therapist after so much JavaScript lol
  - D: Impossible! You shouldn't see a therapist after so much JavaScript lol

101.输出什么?

```javascript
const one = (false || {} || null)
const two = (null || false || “”)
const three = ([] || 0 || true)

console.log(one, two, three)
```

• A: false null []
  - B: null "" true
  - C: {} "" []
  - D: null null true

102. 依次输出什么?

```javascript
const myPromise = () => Promise.resolve(‘I have resolved!’)

function firstFunction() {
myPromise().then(res => console.log(res))
console.log(‘second’)
}

async function secondFunction() {
console.log(await myPromise())
console.log(‘second’)
}

firstFunction()
secondFunction()
```

• A: I have resolved!, second and I have resolved!, second
  - B: second, I have resolved! and second, I have resolved!
  - C: I have resolved!, second and second, I have resolved!
  - D: second, I have resolved! and I have resolved!, second

103. 输出什么?

```javascript
const set = new Set()

set.add(1)
set.add(“Lydia”)
set.add({ name: “Lydia” })

for (let item of set) {
console.log(item + 2)
}
```

• A: 3, NaN, NaN
  - B: 3, 7, NaN
  - C: 3, Lydia2, [Object object]2
  - D: "12", Lydia2, [Object object]2

104. 结果是什么?

javascript<br />Promise.resolve(5)<br />

• A: 5
  - B: Promise {<pending>: 5}
  - C: Promise {<fulfilled>: 5}
  - D: Error

105. 输出什么?

```javascript
function compareMembers(person1, person2 = person) {
if (person1 !== person2) {
console.log(“Not the same!”)
} else {
console.log(“They are the same!”)
}
}

const person = { name: “Lydia” }

compareMembers(person)
```

• A: Not the same!
  - B: They are the same!
  - C: ReferenceError
  - D: SyntaxError

106. 输出什么?

```javascript
const colorConfig = {
red: true,
blue: false,
green: true,
black: true,
yellow: false,
}

const colors = [“pink”, “red”, “blue”]

console.log(colorConfig.colors[1])
```

• A: true
  - B: false
  - C: undefined
  - D: TypeError

107. 输出什么?

javascript<br />console.log('❤️' === '❤️')<br />

• A: true
  - B: false

108. 哪些方法修改了原数组?

```javascript
const emojis = [‘✨’, ‘🥑’, ‘😍’]

emojis.map(x => x + ‘✨’)
emojis.filter(x => x !== ‘🥑’)
emojis.find(x => x !== ‘🥑’)
emojis.reduce((acc, cur) => acc + ‘✨’)
emojis.slice(1, 2, ‘✨’)
emojis.splice(1, 2, ‘✨’)
```

• A: All of them
  - B: map reduce slice splice
  - C: map slice splice
  - D: splice

109. 输出什么?

```javascript
const food = [‘🍕’, ‘🍫’, ‘🥑’, ‘🍔’]
const info = { favoriteFood: food[0] }

info.favoriteFood = ‘🍝’

console.log(food)
```

• A: ['🍕', '🍫', '🥑', '🍔']
  - B: ['🍝', '🍫', '🥑', '🍔']
  - C: ['🍝', '🍕', '🍫', '🥑', '🍔']
  - D: ReferenceError

110. 这个函数干了什么?

javascript<br />JSON.parse()<br />

• A: Parses JSON to a JavaScript value
  - B: Parses a JavaScript object to JSON
  - C: Parses any JavaScript value to JSON
  - D: Parses JSON to a JavaScript object only

111. 输出什么?

```javascript
let name = ‘Lydia’

function getName() {
console.log(name)
let name = ‘Sarah’
}

getName()
```

• A: Lydia
  - B: Sarah
  - C: undefined
  - D: ReferenceError

112. 输出什么？

```javascript
function* generatorOne() {
yield [‘a’, ‘b’, ‘c’];
}

function generatorTwo() {
yield [‘a’, ‘b’, ‘c’];
}

const one = generatorOne()
const two = generatorTwo()

console.log(one.next().value)
console.log(two.next().value)
```

• A: a and a
  - B: a and undefined
  - C: ['a', 'b', 'c'] and a
  - D: a and ['a', 'b', 'c']

113. 输出什么？

javascript<br />console.log(`${(x => x)('I love')} to program`)<br />

• A: I love to program
  - B: undefined to program
  - C: ${(x => x)('I love') to program
  - D: TypeError

114. 将会发生什么?

```javascript
let config = {
alert: setInterval(() => {
console.log(‘Alert!’)
}, 1000)
}

config = null
```

• A: setInterval 的回调不会被调用
  - B: setInterval 的回调被调用一次
  - C: setInterval 的回调仍然会被每秒钟调用
  - D: 我们从没调用过 config.alert(), config 为 null

115. 哪一个方法会返回 'Hello world!' ？

```javascript
const myMap = new Map()
const myFunc = () => ‘greeting’

myMap.set(myFunc, ‘Hello world!’)

//1
myMap.get(‘greeting’)
//2
myMap.get(myFunc)
//3
myMap.get(() => ‘greeting’)
```

• A: 1
  - B: 2
  - C: 2 and 3
  - D: All of them

116. 输出什么？

```javascript
const person = {
name: “Lydia”,
age: 21
}

const changeAge = (x = { …person }) => x.age += 1
const changeAgeAndName = (x = { …person }) => {
x.age += 1
x.name = “Sarah”
}

changeAge(person)
changeAgeAndName()

console.log(person)
```

• A: {name: "Sarah", age: 22}
  - B: {name: "Sarah", age: 23}
  - C: {name: "Lydia", age: 22}
  - D: {name: "Lydia", age: 23}

117. 下面那个选项将会返回 6?

javascript<br />function sumValues(x, y, z) {<br /> return x + y + z;<br />}<br />

• A: sumValues([...1, 2, 3])
  - B: sumValues([...[1, 2, 3]])
  - C: sumValues(...[1, 2, 3])
  - D: sumValues([1, 2, 3])

118. 输出什么？

```javascript
let num = 1;
const list = [“🥳”, “🤠”, “🥰”, “🤪”];

console.log(list[(num += 1)]);
```

• A: 🤠
  - B: 🥰
  - C: SyntaxError
  - D: ReferenceError

119. 输出什么？

``javascript<br />const person = {<br /> firstName: "Lydia",<br /> lastName: "Hallie",<br /> pet: {<br /> name: "Mara",<br /> breed: "Dutch Tulip Hound"<br /> },<br /> getFullName() {<br /> return${this.firstName} ${this.lastName}`;
}
};

console.log(person.pet?.name);
console.log(person.pet?.family?.name);
console.log(person.getFullName?.());
console.log(member.getLastName?.());
```

• A: undefined undefined undefined undefined
  - B: Mara undefined Lydia Hallie ReferenceError
  - C: Mara null Lydia Hallie null
  - D: null ReferenceError null ReferenceError

120. 输出什么？

```javascript
const groceries = [“banana”, “apple”, “peanuts”];

if (groceries.indexOf(“banana”)) {
console.log(“We have to buy bananas!”);
} else {
console.log(We don't have to buy bananas!);
}
```

• A: We have to buy bananas!
  - B: We don’t have to buy bananas
  - C: undefined
  - D: 1

121. 输出什么?

```javascript
const config = {
languages: [],
set language(lang) {
return this.languages.push(lang);
}
};

console.log(config.language);
```

• A: function language(lang) { this.languages.push(lang }
  - B: 0
  - C: []
  - D: undefined

122. 输出什么？

```javascript
const name = “Lydia Hallie”;

console.log(!typeof name === “object”);
console.log(!typeof name === “string”);
```

• A: false true
  - B: true false
  - C: false false
  - D: true true

123. 输出什么?

```javascript
const add = x => y => z => {
console.log(x, y, z);
return x + y + z;
};

add(4)(5)(6);
```

• A: 4 5 6
  - B: 6 5 4
  - C: 4 function function
  - D: undefined undefined 6

124. 输出什么？

```javascript
async function* range(start, end) {
for (let i = start; i <= end; i++) {
yield Promise.resolve(i);
}
}

(async () => {
const gen = range(1, 3);
for await (const item of gen) {
console.log(item);
}
})();
```

• A: Promise {1} Promise {2} Promise {3}
  - B: Promise {<pending>} Promise {<pending>} Promise {<pending>}
  - C: 1 2 3
  - D: undefined undefined undefined

125. 输出什么？

```javascript
const myFunc = ({ x, y, z }) => {
console.log(x, y, z);
};

myFunc(1, 2, 3);
```

• A: 1 2 3
  - B: {1: 1} {2: 2} {3: 3}
  - C: { 1: undefined } undefined undefined
  - D: undefined undefined undefined

126. 输出什么？

```javascript
function getFine(speed, amount) {
const formattedSpeed = new Intl.NumberFormat(
‘en-US’,
{ style: ‘unit’, unit: ‘mile-per-hour’ }
).format(speed)

const formattedAmount = new Intl.NumberFormat(
‘en-US’,
{ style: ‘currency’, currency: ‘USD’ }
).format(amount)

return The driver drove ${formattedSpeed} and has to pay ${formattedAmount}
}

console.log(getFine(130, 300))
```

• A: The driver drove 130 and has to pay 300
  - B: The driver drove 130 mph and has to pay \$300.00
  - C: The driver drove undefined and has to pay undefined
  - D: The driver drove 130.00 and has to pay 300.00

127. 输出什么？

```javascript
const spookyItems = [“👻”, “🎃”, “🕸”];
({ item: spookyItems[3] } = { item: “💀” });

console.log(spookyItems);
```

• A: ["👻", "🎃", "🕸"]
  - B: ["👻", "🎃", "🕸", "💀"]
  - C: ["👻", "🎃", "🕸", { item: "💀" }]
  - D: ["👻", "🎃", "🕸", "[object Object]"]

128. 输出什么？

```javascript
const name = “Lydia Hallie”;
const age = 21;

console.log(Number.isNaN(name));
console.log(Number.isNaN(age));

console.log(isNaN(name));
console.log(isNaN(age));
```

• A: true false true false
  - B: true false false false
  - C: false false true false
  - D: false true false true

129. 输出什么？

```javascript
const randomValue = 21;

function getInfo() {
console.log(typeof randomValue);
const randomValue = “Lydia Hallie”;
}

getInfo();
```

• A: "number"
  - B: "string"
  - C: undefined
  - D: ReferenceError

130. 输出什么？

```javascript
const myPromise = Promise.resolve(“Woah some cool data”);

(async () => {
try {
console.log(await myPromise);
} catch {
throw new Error(Oops didn't work);
} finally {
console.log(“Oh finally!”);
}
})();
```

• A: Woah some cool data
  - B: Oh finally!
  - C: Woah some cool data Oh finally!
  - D: Oops didn't work Oh finally!

131. 输出什么？

```javascript
const emojis = [“🥑”, [“✨”, “✨”, [“🍕”, “🍕”]]];

console.log(emojis.flat(1));
```

• A: ['🥑', ['✨', '✨', ['🍕', '🍕']]]
  - B: ['🥑', '✨', '✨', ['🍕', '🍕']]
  - C: ['🥑', ['✨', '✨', '🍕', '🍕']]
  - D: ['🥑', '✨', '✨', '🍕', '🍕']

132. 输出什么？

```javascript
class Counter {
constructor() {
this.count = 0;
}

increment() {<br />        this.count++;<br />    }<br />}

const counterOne = new Counter();
counterOne.increment();
counterOne.increment();

const counterTwo = counterOne;
counterTwo.increment();

console.log(counterOne.count);
```

• A: 0
  - B: 1
  - C: 2
  - D: 3

133. 输出什么？

```javascript
const myPromise = Promise.resolve(Promise.resolve(“Promise!”));

function funcOne() {
myPromise.then(res => res).then(res => console.log(res));
setTimeout(() => console.log(“Timeout!”), 0);
console.log(“Last line!”);
}

async function funcTwo() {
const res = await myPromise;
console.log(await res);
setTimeout(() => console.log(“Timeout!”), 0);
console.log(“Last line!”);
}

funcOne();
funcTwo();
```

• A: Promise! Last line! Promise! Last line! Last line! Promise!
  - B: Last line! Timeout! Promise! Last line! Timeout! Promise!
  - C: Promise! Last line! Last line! Promise! Timeout! Timeout!
  - D: Last line! Promise! Promise! Last line! Timeout! Timeout!

134. 我们怎样才能在 index.js 中调用 sum.js? 中的 sum？

```javascript
// sum.js
export default function sum(x) {
return x + x;
}

// index.js
import * as sum from “./sum”;
```

• A: sum(4)
  - B: sum.sum(4)
  - C: sum.default(4)
  - D: 默认导出不用 * 来导入，只能具名导出

135. 输出什么？

```javascript
const handler = {
set: () => console.log(“Added a new property!”),
get: () => console.log(“Accessed a property!”)
};

const person = new Proxy({}, handler);

person.name = “Lydia”;
person.name;
```

• A: Added a new property!
  - B: Accessed a property!
  - C: Added a new property! Accessed a property!
  - D: 没有任何输出

136. 以下哪一项会对对象 person 有副作用？

```javascript
const person = { name: “Lydia Hallie” };

Object.seal(person);
```

• A: person.name = "Evan Bacon"
  - B: person.age = 21
  - C: delete person.name
  - D: Object.assign(person, { age: 21 })

137. 以下哪一项会对对象 person 有副作用？

```javascript
const person = {
name: “Lydia Hallie”,
address: {
street: “100 Main St”
}
};

Object.freeze(person);
```

• A: person.name = "Evan Bacon"
  - B: delete person.address
  - C: person.address.street = "101 Main St"
  - D: person.pet = { name: "Mara" }

138. 输出什么？

```javascript
const add = x => x + x;

function myFunc(num = 2, value = add(num)) {
console.log(num, value);
}

myFunc();
myFunc(3);
```

• A: 2 4 and 3 6
  - B: 2 NaN and 3 NaN
  - C: 2 Error and 3 6
  - D: 2 4 and 3 Error

139. 输出什么？

```javascript
class Counter {
#number = 10

increment() {
this.#number++
}

getNum() {
return this.#number
}
}

const counter = new Counter()
counter.increment()

console.log(counter.#number)
```

• A: 10
  - B: 11
  - C: undefined
  - D: SyntaxError

140. 选择哪一个？

```javascript
const teams = [
{ name: “Team 1”, members: [“Paul”, “Lisa”] },
{ name: “Team 2”, members: [“Laura”, “Tim”] }
];

function* getMembers(members) {
for (let i = 0; i < members.length; i++) {
yield members[i];
}
}

function* getTeams(teams) {
for (let i = 0; i < teams.length; i++) {
// ✨ SOMETHING IS MISSING HERE ✨
}
}

const obj = getTeams(teams);
obj.next(); // { value: “Paul”, done: false }
obj.next(); // { value: “Lisa”, done: false }
```

• A: yield getMembers(teams[i].members)
  - B: yield* getMembers(teams[i].members)
  - C: return getMembers(teams[i].members)
  - D: return yield getMembers(teams[i].members)

141. 输出什么？

```javascript
const person = {
name: “Lydia Hallie”,
hobbies: [“coding”]
};

function addHobby(hobby, hobbies = person.hobbies) {
hobbies.push(hobby);
return hobbies;
}

addHobby(“running”, []);
addHobby(“dancing”);
addHobby(“baking”, person.hobbies);

console.log(person.hobbies);
```

• A: ["coding"]
  - B: ["coding", "dancing"]
  - C: ["coding", "dancing", "baking"]
  - D: ["coding", "running", "dancing", "baking"]

142. 输出什么？

```javascript
class Bird {
constructor() {
console.log(“I’m a bird. 🦢”);
}
}

class Flamingo extends Bird {
constructor() {
console.log(“I’m pink. 🌸”);
super();
}
}

const pet = new Flamingo();
```

• A: I'm pink. 🌸
  - B: I'm pink. 🌸 I'm a bird. 🦢
  - C: I'm a bird. 🦢 I'm pink. 🌸
  - D: Nothing, we didn’t call any method

143. 哪一个选项会导致报错？

```javascript
const emojis = [“🎄”, “🎅🏼”, “🎁”, “⭐”];

/ 1 / emojis.push(“🦌”);
/ 2 / emojis.splice(0, 2);
/ 3 / emojis = […emojis, “🥂”];
/ 4 / emojis.length = 0;
```

• A: 1
  - B: 1 and 2
  - C: 3 and 4
  - D: 3

144. 我们需要向对象 person 添加什么，以致执行 [...person] 时获得形如 ["Lydia Hallie", 21] 的输出？

```javascript
const person = {
name: “Lydia Hallie”,
age: 21
}

[…person] // [“Lydia Hallie”, 21]
```

• A: 不需要，对象默认就是可迭代的
  - B: *[Symbol.iterator]() { for (let x in this) yield* this[x] }
  - C: *[Symbol.iterator]() { yield* Object.values(this) }
  - D: *[Symbol.iterator]() { for (let x in this) yield this }

145. 输出什么？
```javascript
let count = 0;
const nums = [0, 1, 2, 3];

nums.forEach(num => {
if (num) count += 1
})

console.log(count)
```

• A: 1
  - B: 2
  - C: 3
  - D: 4
  
  答案

  
  

答案: C

在 forEach 循环内部的 if 会判断 num 的值是truthy或者是falsy。因为 nums 数组的第一个数字是 0，一个falsy值， if 语句代码块不会被执行。count 仅仅在 nums 数组的其他3个数字 1，2，3 时加1。因为 count 执行了3次加 1 运算，所以 count 的值为 3。

146. 输出是什么？

```javascript
function getFruit(fruits) {
console.log(fruits?.[1]?.[1])
}

getFruit([[‘🍊’, ‘🍌’], [‘🍍’]])
getFruit()
getFruit([[‘🍍’], [‘🍊’, ‘🍌’]])
```

• A: null, undefined, 🍌
  - B: [], null, 🍌
  - C: [], [], 🍌
  - D: undefined, undefined, 🍌

147. 输出什么？

```javascript
class Calc {
constructor() {
this.count = 0
}

increase() {<br />        this.count ++<br />    }<br />}

const calc = new Calc()
new Calc().increase()

console.log(calc.count)
```

• A: 0
  - B: 1
  - C: undefined
  - D: ReferenceError

148. 输出什么?

```javascript
const user = {
email: “e@mail.com”,
password: “12345”
}

const updateUser = ({ email, password }) => {
if (email) {
Object.assign(user, { email })
}

if (password) {<br />        user.password = password<br />    }
return user<br />}

const updatedUser = updateUser({ email: “new@email.com” })

console.log(updatedUser === user)
```

• A: false
  - B: true
  - C: TypeError
  - D: ReferenceError

149. 输出什么?

```javascript
const fruit = [‘🍌’, ‘🍊’, ‘🍎’]

fruit.slice(0, 1)
fruit.splice(0, 1)
fruit.unshift(‘🍇’)

console.log(fruit)
```

• A: ['🍌', '🍊', '🍎']
  - B: ['🍊', '🍎']
  - C: ['🍇', '🍊', '🍎']
  - D: ['🍇', '🍌', '🍊', '🍎']

150. 输出什么?

```javascript
const animals = {};
let dog = { emoji: ‘🐶’ }
let cat = { emoji: ‘🐈’ }

animals[dog] = { …dog, name: “Mara” }
animals[cat] = { …cat, name: “Sara” }

console.log(animals[dog])
```

• A: { emoji: "🐶", name: "Mara" }
  - B: { emoji: "🐈", name: "Sara" }
  - C: undefined
  - D: ReferenceError

151. 输出什么?

```javascript
const user = {
email: “my@email.com”,
updateEmail: email => {
this.email = email
}
}

user.updateEmail(“new@email.com”)
console.log(user.email)
```

• A: my@email.com
  - B: new@email.com
  - C: undefined
  - D: ReferenceError

152. 输出什么?

```javascript
const promise1 = Promise.resolve(‘First’)
const promise2 = Promise.resolve(‘Second’)
const promise3 = Promise.reject(‘Third’)
const promise4 = Promise.resolve(‘Fourth’)

const runPromises = async () => {
const res1 = await Promise.all([promise1, promise2])
const res2 = await Promise.all([promise3, promise4])
return [res1, res2]
}

runPromises()
.then(res => console.log(res))
.catch(err => console.log(err))
```

• A: [['First', 'Second'], ['Fourth']]
  - B: [['First', 'Second'], ['Third', 'Fourth']]
  - C: [['First', 'Second']]
  - D: 'Third'

153. 哪个作为method的值可以打印{ name: "Lydia", age: 22 }?

```javascript
const keys = [“name”, “age”]
const values = [“Lydia”, 22]

const method = / ?? /
Objectmethod => {
return [keys[i], values[i]]
})) // { name: “Lydia”, age: 22 }
```

• A: entries
  - B: values
  - C: fromEntries
  - D: forEach

154. 输出什么?

```javascript
const createMember = ({ email, address = {}}) => {
const validEmail = /.+\@.+..+/.test(email)
if (!validEmail) throw new Error(“Valid email pls”)

return {<br />        email,<br />        address: address ? address : null<br />    }<br />}

const member = createMember({ email: “my@email.com” })
console.log(member)
```

• A: { email: "my@email.com", address: null }
  - B: { email: "my@email.com" }
  - C: { email: "my@email.com", address: {} }
  - D: { email: "my@email.com", address: undefined }

155. 输出什么?

```javascript
let randomValue = { name: “Lydia” }
randomValue = 23

if (!typeof randomValue === “string”) {
console.log(“It’s not a string!”)
} else {
console.log(“Yay it’s a string!”)
}
```

• A: It's not a string!
  - B: Yay it's a string!
  - C: TypeError
  - D: undefined