详细学习链接: http://es6.ruanyifeng.com/#docs/let let命令 基本用法 ES6新增了let命令,用来声明变量.它的用法类似于var,但是所声明的变量,只在let命令所在的代码块内有效. 'use strict'; { let a = 10; var b = 1; } a // 报错,ReferenceError: a is not defined. b // 1 不存在变量提升 let不像var那样会发生"变量提升"现象.所以,变量一定要在声明后使…
1.let命令(作用同var) ES6新增了let命令,用来声明变量.它的用法类似于var,但是所声明的变量,只在let命令所在的代码块内有效. { let a = 10; var b = 1; } a // ReferenceError: a is not defined. b // 1 上面代码在代码块之中,分别用let和var声明了两个变量.然后在代码块之外调用这两个变量,结果let声明的变量报错,var声明的变量返回了正确的值.这表明,let声明的变量只在它所在的代码块有效. for循环…
Before you learn about dependency injection and Unity, you need to understand why you should use them. And in order to understand why you should use them, you should understand what types of problems dependency injection and Unity are designed to hel…
1.Symbol,一个每次创建都不一样的值 Symbol undefined null Boolean String Number Object let c=Symbol("这是一个Symbol"); let a=Symbol(); let b=Symbol(); console.log("a:",a); console.log("b:",b); console.log("c:",c);console.log(a===b);…
