方法1 定義方法clone

function clone(obj) {
  let copy;
  if (obj instanceof Array) {
    copy = [];
    let i = obj.length;
    while (i--) {
      copy[i] = clone(obj[i]);
    }
    return copy;
  } else if (obj instanceof Object) {
    copy = {};
    for (let k in obj) {
      copy[k] = clone(obj[k]);
    }
    return copy;
  } else {
    return obj;
  }
}

方法1缺點(diǎn)：無法拷貝函數(shù)

方法2 使用 JSON.stringify 和 JSON.parse 方法

var arr = ['old', 1, true, ['old1', 'old2'], {old: 1}]
var new_arr = JSON.parse( JSON.stringify(arr));
console.log(new_arr);   //  [ 'old', 1, true, [ 'old1', 'old2' ], { old: 1 } ]

方法2缺點(diǎn)：同樣無法拷貝函數(shù)

方法3 定義deepClone函數(shù)

function deepClone(source) {
  // 遞歸終止條件
  if (!source || typeof source !== 'object') {
    return source;
  }
  var targetObj = source instanceof Array ? [] : {};
  for (var key in source) {
    // 該方法會(huì)忽略掉那些從原型鏈上繼承到的屬性。
    if (source.hasOwnProperty(key)){
    // 避免死循環(huán)對(duì)象屬性
      if(source[key] === source){
        console.warn(new Error('circular object'))
      }else if (source[key] && typeof source[key] === 'object') {  //數(shù)組 typeof的結(jié)果也是object
        targetObj[key] = deepClone(source[key]);
      } else {
        targetObj[key] = source[key];
      }
    }
  }
  return targetObj;
}
var object1 = {'year':12, arr: [1, 2, 3], obj: {key: 'value' }, func: function(){return 1;}};
var object2 = [1,[2,[3,4,[5,6]]]]
var newObj= deepClone(object1);
var newObj2 = deepClone(object2)
console.log(newObj)  // { year: 12,arr: [ 1, 2, 3 ],obj: { key: 'value' }, func: [Function: func] }
console.log(newObj2) // [ 1, [ 2, [ 3, 4, [Array] ] ] ]