Array from a string

  1. Array.from('foo'); 
  2. // [ "f", "o", "o" ]

Array from a set

  1. const set = new Set(['foo', 'bar', 'baz', 'foo']);
  2. Array.from(set);
  3. // [ "foo", "bar", "baz" ]

Array from a map

  1. const map = new Map([[1, 2], [2, 4], [4, 8]]);
  2. Array.from(map);
  3. // [[1, 2], [2, 4], [4, 8]]
  5. const mapper = new Map([['1', 'a'], ['2', 'b']]);
  6. Array.from(mapper.values());
  7. // ['a', 'b'];
  9. Array.from(mapper.keys());
  10. // ['1', '2'];

Array from an Array-like obj(类数组对象)

  1. function f() {
  2.   return Array.from(arguments);
  3. }
  5. f(1, 2, 3);
  7. // [ 1, 2, 3 ]

Using arrow functions and Array.from()

  1. // Using an arrow function as the map function to
  2. // manipulate the elements
  3. Array.from([1, 2, 3], x => x + x);      
  4. // [2, 4, 6]
  7. // Generate a sequence of numbers
  8. // Since the array is initialized with `undefined` on each position,
  9. // the value of `v` below will be `undefined`
  10. Array.from({length: 5}, (v, i) => i);
  11. // [0, 1, 2, 3, 4]

使用对象填充数组

  1. const length = 3;
  2. const resultA = Array.from({ length }, () => ({}));
  3. const resultB = Array(length).fill({});
  5. resultA; // => [{}, {}, {}]
  6. resultB; // => [{}, {}, {}]
  8. resultA[0] === resultA[1]; // => false
  9. resultB[0] === resultB[1]; // => true

克隆一个数组

  1. const numbers = [3, 6, 9];
  2. const numbersCopy = Array.from(numbers);
  4. numbers === numbersCopy; // => false