<!DOCTYPE html>
<html>
<head>
<title>aa</title>
</head>
<body>
<button onclick="myFunction()">点我可查看这一串"start,start,end,person,people,velocity,start"字符中"start"字符出现的次数</button>
<p id="demo"></p>
<script type="text/javascript">
function myFunction(){
var str = "start,start,end,person,people,velocity,start";
var count=0;
var index=0;
var key="start";
while((index = str.indexOf(key,index))!= -1){
index += key.length;
count = count+1;
}
document.getElementById("demo").innerHTML = count;
}
</script>
</body>
</html>
原文：https://www.cnblogs.com/yyh187/p/9835689.html