js--计算数组中重复出现元素的个数

    //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}