javascript map用法实例

map() 方法创建一个新数组，其结果是该数组中的每个元素都调用一个提供的函数后返回的结果。也就是原数组“映射”成对应新数组，调用的函数就是映射函数。

map()内部实现：

Array.prototype.map = function(fun /*, thisp*/){  var len = this.length;  if (typeof fun != "function")    throw new TypeError();  var res = new Array(len);  var thisp = arguments[1];  for (var i = 0; i < len; i++)  {    if (i in this)      res[i] = fun.call(thisp, this[i], i, this);  }  return res;};

具体实例：

1.普通数组：

var data = [1, 2, 3, 4];var  newData = data.map(function(i){return i*i});console.log(newData)

结果：[1, 4, 9, 16]

2.json数组

var json = [{"id":21202,"bondId":21202,"market":"上交所","hypCode":"shzfz01","hypAbb":"上海政府债01","enterDate":"2014-05-14","createTime":1506756153000,"updateTime":1506756153000,"operator":"admin"},{"id":21203,"bondId":21202,"market":"北金所","hypCode":"shzfz01","hypAbb":"上海政府债01","enterDate":"2014-05-16","createTime":1506756153000,"updateTime":1506756153000,"operator":"admin"}];var newJson = json.map((us)=>{return {newbondId:us.bondId,newmarket:us.market,newhypCode:us.hypCode}});console.log(newJson);

结果：

1. [{newbondId:21202,
2. newhypCode:"shzfz01",
3. newmarket:"上交所"},
4. 
   
1. {newbondId:21202,
2. newhypCode:"shzfz01",
3. newmarket:"北金所"}]