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