js根据需要计算数组中重复出现某个元素的个数

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！

总结