# Type Script

ES是脚本语言的规划 JavaScript ES5 TypeScript ES6

学习TypeScript的好处

## 安装TypeScript开发环境

compiler 使用在线compiler开发 本地compiler npm node package manage 使用npm安装ts：npm install -g typescript 将ts文件编译为js文件：tsc hello.ts

## 字符串新特性

多行字符串 双撇号 \`\` 字符串模板 ${ } 只有在双撇号中才有用 自动拆分字符串

## TypeScript参数类型

* any string number boolean 
* void 用于声明返回值
* 自定义类型

用：赋类型

```typescript
var myname:string="xxx"



class Person{
    name:string;
    age:number;
}
```

TypeSctipt参数默认值

* 变量默认值
* 方法默认值

    带默认值的参数要放在最后

```typescript
function test(a:string,b:string,c:string="jojo"){
    console.log(a);
}

test("xxx")
```

可选参数 用问号设置参数为默认值 可选参数需要申明在必选参数之后

> 注意：使用可选时，要处理可选参数为空的情况

```typescript
function test(a:string,b?:string){

}
```

## Rest and Spread操作符

任意数量的参数 ...args

```typescript
function fun1(...args){
    args.foreach(function(arg){
        console.log(arg)
    })
}
```

## generator函数

手动暂停和恢复代码执行 TypeScript编译器： babel

```typescript
function* dosomething(){
    console.log("start")
    yield
    concole.log("finish")
}

var func1=doSomething()
func1.next()
```

析构表达式 用法一：从对象中取值 用{} 使用 别名 嵌套

```typescript
function getStock(){
    return{
        code:"IBM"
        price:100
        prices:{
            price1:200,
            price2：300
        }
    }
}
var{code,price}=getStock();
var{code:codex,price}=getStock();
var{code,price,prices:{price1}}=getStock();
console.log(code);
console.log(price);
```

用法二：从数组中取值 用\[]

```typescript
var [number1,bumber2,...others]=array1
```

用法三：当参数

## 箭头表达式

\=> 代替了function 用来声明匿名表达式，

javaScript this关键字

```typescript
var sum=(arg1,arg2)=>arg1+arg2;

var sum =()=>{

}

var sum=arg1=>{

}
```

for of 循环

```typescript
var myArray={1,2,3,4};
myArray.desc="four number"

myArray.forEach(value=>console.log(value))


//  n其实是key JavaScript
for(var n in myArray){
    console.log(n);
    console.log(myArray[n])
}

// 忽略属性 n是value
for(var n of myArray){
   if(n>2) break;
   console.log(n)
}
```

## 类

访问控制符 public private protested

```typescript
class Person{
name;

eat(){
    concole.log("")
}



}

class Employee extends Person{

}




var p1=new Person();
p1.name="batman";
p1.eat();
```

## 类型定义文件

\*.d.ts 在ts用js工具包

typings


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