js中判断一个字符在字符串中出现的次数，方法有哪些

Question

查找字母e出现的次数：

let str = "hello everyone";

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如题，我目前想到的方法有：

1. 使用split方法let num = str.split('e').length -1; num ==> 4

2. 使用match方法（全局检索）let reg = /e/g; let num = str.match(reg).length; num ==> 4

还有其他方法吗？

Answer 1

用传统的indexof呗，然后循环遍历查找

Answer 2

let str='hello everyone';function catStr(str){&nbsp; &nbsp; ler num=0;&nbsp; &nbsp; for(var i=0,len=str.length;i<len;i++){&nbsp; &nbsp; &nbsp; &nbsp; if(str[i]=='e'){&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; num++&nbsp; &nbsp; &nbsp; &nbsp; }&nbsp; &nbsp; }return num}catStr(str)for是最省性能的

Answer 3

var strs = "hello everyone"&nbsp;var num = strs.split('').filter(i => i == 'e').length&nbsp;// 4

Answer 4

超级快！console.time('start');let num = 0;let str = "hello everyone"while(str.indexOf('e')!== -1) {&nbsp; &nbsp; str = str.slice(str.indexOf('e') + 1)&nbsp; &nbsp; num += 1}console.timeEnd('start')start: 0.024658203125ms