let 局部变量声明
var arr = [1,2,3];
for(let i of arr){
console.log(i); //1,2,3
}
const 常量声明
特征 声明后不能修改 否则报错
const i = 2;
i = 3; // 报错 Uncaught TypeError: Assignment to constant variable.
var arr = [1,2,3];
for(let i of arr){
console.log(i); //1,2,3
}
const i = 2;
i = 3; // 报错 Uncaught TypeError: Assignment to constant variable.