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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