请教下javascript说如何利用indexOF()函数统计数组的？

Question

利用indexOF()函数统计数组arr("a","b","d","d","c","d","d")中元素d中出现的次数，并同时返回其对应的所有下标这道题

Answer 1

function f(i,  indexes){        var j = arr.indexOf('d', i);        if(j == -1) return  indexes;        indexes.push(j);        return f(++j, indexes);} var arr = ["a","b","d","d","c","d","d"];var  indexes = f(0, []);console.log("'d' 出现了：" + indexes.length + "次， 下标为：" + indexes);

Answer 2

var&nbsp;results&nbsp;=&nbsp;[];&nbsp;var&nbsp;fromIndex&nbsp;=&nbsp;0;&nbsp;var&nbsp;arr&nbsp;=&nbsp;["a","b","d","d","c","d","d"];&nbsp;while(fromIndex<arr.length){&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;index&nbsp;=&nbsp;arr.indexOf('d',fromIndex);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;if(index&nbsp;==&nbsp;-1){&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;break;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;else{&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;results.push(index);&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fromIndex&nbsp;=&nbsp;index&nbsp;+&nbsp;1;&nbsp;&nbsp;&nbsp;&nbsp;}&nbsp;}