JavaScript如何将伪数组转换成数组 

let arrayLike = {
  "0": "a",
  "1": "b",
  "2": "c",
  "length": 3
}

// 通过 makeArray 方法，把数组转成伪数组
function makeArray(arrayLike) {
  let result = [];
  for (let i = 0, len = arrayLike.length; i < len; i++) {
    result.push(arrayLike[i]);
  }
  return result;
}
function doSomething () {
  let args = makeArray(arguments);
  console.log(args);
}
doSomething(1, 2, 3);
// 输出: [1, 2, 3]

function doSomething () {
  let args = Array.prototype.slice.call(arguments);
  console.log(args);
}
doSomething(1, 2, 3);

// 输出: [1, 2, 3]

function doSomething () {
  let args = Array.from(arguments);
  console.log(args);
}
doSomething('一', '二', '三');

// 输出: ['一', '二', '三']

let helper = {
  diff: 1,
  add (value) {
    return value + this.diff; // 注意这里有个 this
  }
};
function translate () {
  return Array.from(arguments, helper.add, helper);
}
let numbers = translate(1, 2, 3);
console.log(numbers); // 2, 3, 4

let array = Array.from({length: 5}, () => 1)
console.log(array)

// 输出: [1, 1, 1, 1, 1]

let msg = 'hello';
let msgArr = Array.from(msg);
console.log(msgArr);

// 输出: ["h", "e", "l", "l", "o"]