ES7

//1. 指数运算符(幂): **
    console.log(3 ** 3);//27
//2. Array.prototype.includes(value) : 判断数组中是否包含指定value
    let arr = [1,2,3,4, 'abc'];
    console.log(arr.includes(2));//true
    console.log(arr.includes(5));//false