ES6新特性_变量声明let

ES6 let 声明变量

    let a;
    let b,c,d;
    let e = 100;
    let f = 200, g = 300, h = [];

ES6 let 新特性1 变量不能重复声明

    let name = '张三';
    let name = '李四';
    
    // 如果重复声明：则控制台会报错：Uncaught SyntaxError: Identifier 'name' has already been declared


    // var 可重复声明
    var name = "王五";
    var name = "赵六";
    console.log(name);

ES6 let 新特性2 块儿级作用域

    {
        let age = 22;
    }
    // 在大括号外打印
    console.log(age) // Uncaught ReferenceError: age is not defined

ES6 let 新特性3 不存在变量提升

    console.log(h); // Uncaught ReferenceError: Cannot access 'h' before initialization
    let h = 1.88;
    console.log(h); // 1.88

ES6 let 块儿级作用域，但不影响作用域链

{
    let n = 'nnnnn';
    function func(){
        console.log(n); // 打印n
    }
    func();
}