javascript - 切割json出错

Question

我要根据state分组，然后报错了。

var json = [
    {"state": 0, "name": "xxxx"},
    {"state": 1, "name": "cccc"},
    {"state": 2, "name": "zzzz"},
    {"state": 3, "name": "hhhh"}
]

function sortjson(json){
  var i,l,n,
      a1 = [],a2=[],a3=[],a4=[];
    for(i=0,l=json.length;i<l;i++){
       switch( json[i].state){
          case 0:
             a1.push(json.splice(i,1))
             break;
          case 1:
             a2.push(json.splice(i,1))
             break;
          case 2:
             a3.push(json.splice(i,1))
             break;
          case 3:
             a4.push(json.splice(i,1))
             break;
       }
    }
   return {
      a1:a1,a2:a2,a3:a3,a4:a4
   }
}

报错 Uncaught TypeError: Cannot read property 'state' of undefined

Answer 1

因为每个 loop 都 splice 了初始数组，数组里的项越来越少。到第三次循环就 undefined，第四次就直接抛异常了。
你自己在 switch 之前 console.log(json, i) 对比下看看：

Answer 2

Array.prototype.sortjson = function () {
    [1,2,3,4].forEach(function(number){window['a'+number] = []});
    this.forEach(function(item){window['a'+(item.state+1)].push(item)});
    return {a1:a1, a2:a2, a3:a3, a4:a4};
}

console.log([
    {"state": 0, "name": "xxxx"},
    {"state": 1, "name": "cccc"},
    {"state": 2, "name": "zzzz"},
    {"state": 3, "name": "hhhh"}
].sortjson());

写完这段代码之后想起了今天同学给我讲的笑话：“难怪程序员找不到女朋友，因为他们都喜欢又精又快又短“，再此写上以博诸君一笑。