typescript study

create-data: 2019-11-28 16:14:02
author     : yuyuanqiu
version    : v0.0.1-alpha

handbook

basic types

• boolean
• number
  • numbers are floating-point values
  • support hex, decimal, binary and octal
• string
  • use double, single quotes
  • use backtick/backquote for template strings, and embed expressions using ${ expr }
• array
  • using []
  • using generic array type like Array<elemType>
• tuple
  • an array with a fixed number and known type of elements
  • elements need not be same
  • access an outside of indices fails with an error

let isDone: boolean = false;
let decimal: number = 6;
let hex: number = 0xf00d;
let binary: number = 0b1010;
let octal: number = 0o744;
let color: string = "blue";
color = 'red';
let fullName: string = `Bob Bobbington`;
let age: number = 37;
let sentence: string = `Hello, my name is ${ fullName }.
I'll be ${ age + 1 } years old next month.`;
// equivalent like so:
let sentence: string = "Hello, my name is " + fullName + ".\n\n" + 
    "I'll be " + (age + 1) + " years old next month.";
let list: number[] = [1, 2, 3];
let list: Array<number> = [1, 2, 3];
// declare a tuple type
let x: [string, number];
// initialize it
x = ["hello", 10];  // ok
// initialize it incorrectly
x = [10, "hello"];  // error
console.log(x[0].substring(1)); // ok
console.log(x[1].substring(1)); // error, "number" does not have "substring"
x[3] = "world"; // error, property "3" does not exist on type "[string, number]".
console.log(x[5].toString());   // error, property "5" does not exist on type "[string, number]".