一、有时候的根据需要需要计算数组中某个元素重复出现的个数
var arr = ["apple","orange","apple","orange","pear","orange"];
计算出来重复出现的元素个数:{apple: 2, orange: 3, pear: 1}
二、代码实现
  //统计一个数组中有多少个不重复的单词:  // 不用reduce时:   var arr = ["apple","orange","apple","orange","pear","orange"];   function getWordCnt(){     var obj = {};     for(var i= 0, l = arr.length; i< l; i++){       var item = arr[i];       obj[item] = (obj[item] +1 ) || 1;     }     return obj;   }  console.log(getWordCnt());//{apple: 2, orange: 3, pear: 1}  // 用reduce时:   var arr = ["apple","orange","apple","orange","pear","orange"];   function getWordCnt(){     return arr.reduce(function(prev,next){       prev[next] = (prev[next] + 1) || 1;       return prev;     },{});   }   console.log(getWordCnt());//{apple: 2, orange: 3, pear: 1}补充知识点:
若查询对象中某个属性没有,可自行为其添加
  var muziObj = {};  muziObj['name'] = 'muzidigbig';  muziObj.age = 21;  console.log(muziObj)//{name: "muzidigbig", age: 21}若有不足请多多指教!希望给您带来帮助!
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