Install Node.js environment

https://nodejs.org/en

The version number can be found in the terminal, which means the installation is successful.

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Then, Terminal executes npm i typescript -gInstall TypeScript.

If the version number is found, the installation is successful.

string type

let str:string = "Hello";
console.log(str);

Execute first in the terminal tsc --init, then execute tsc -w. It was found that there was only index.ts in the original TS folder, but now there are two more files.

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Open another terminal and execute

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to output.

Template strings are also supported:

let num:number = 12
let str:string = `${
      
      num}`
console.log(str);

number type

let notANumber: number = NaN;//Nan
let num: number = 123;//普通数字（包括整型和浮点型）
let infinityNumber: number = Infinity;//无穷大
let decimal: number = 6;//十进制
let hex: number = 0xf00d;//十六进制
let binary: number = 0b1010;//二进制
let octal: number = 0o744;//八进制s

Boolean type

// let boolean0:boolean = new Boolean(1) // 此时是对象类型，不是 boolean 类型，要写为以下形式
let createdBoolean: Boolean = new Boolean(1)
let boolean1: boolean = true //可以直接使用布尔值
let boolean2: boolean = Boolean(1) //也可以通过函数返回布尔值

Null and undefined types

let u: undefined = undefined;//定义undefined
let n: null = null;//定义null

void type

let v1:void = null
let v2:void = undefined
// 没有返回值的函数（非严格模式）
function fn(): void {
    
    
  return 
}

let v1:void = nullThere may be errors, you need to set to tsconfig.jsonin , close the strict mode, no more errors. Moreover, in non-strict mode, and can be assigned to each other.strictfalsenullundefined

voidTypes are not assignable to other types, and nulltypes undefinedare assignable to other types. But in strict mode, nullyou cannot assign to voidthe type.

[TypeScript] basic type