1. Array.prototype.slice.call(类数组对象)
   例1： function foo(a, b) {
   let res = Array.prototype.slice.call(arguments);
   console.log(res);
   }

foo('aaa', 'bbb'); //(2) ["aaa", "bbb"]

例2： let json = {
0: 'aaa',
1: 'bbb',
2: 'ccc',
length: 3
}
let res = Array.prototype.slice.call(json);
console.log(res); //(3) ["aaa", "bbb", "ccc"]

2. Array.from(类数组对象)
   例1：function foo(a, b) {
   let res = Array.from(arguments);
   console.log(res);
   }
   foo('aaa', 'bbb'); //(2) ["aaa", "bbb"]

例2： let json = {
0: 'aaa',
1: 'bbb',
2: 'ccc',
length: 3
}
let res = Array.from(json);
console.log(res); //(3) ["aaa", "bbb", "ccc"]

3. 扩展运算符
   例1： function foo(a, b) {
   let res = [...arguments];
   console.log(res);
   }
   foo('aaa', 'bbb'); //(2) ["aaa", "bbb"]

注：扩展运算符不能将json格式的类数组对象转化成数组！！！

   let json = {
        0: 'aaa',
        1: 'bbb',
        2: 'ccc',
        length: 3
    }
    let res = [...json];
    console.log(res);     Uncaught TypeError: json is not iterable at 类数组转数组.html:22