<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
</head>
<body>
<script>
var count = 0;
var stopposition = 0
var item = "stop"
var str = "start,stop,speed,start,stop,speed,start,stop,speed,start,stop,speed,"
while( stopposition < str.length ){
if( str.indexOf( item , stopposition) > 0 ){
count ++
stopposition = str.indexOf( item , stopposition)
stopposition += item.length ;
}else{
stopposition += str.length
}
}
console.log(str)
console.log( '个数为', count );
</script>
</body>
</html>
正则的基本表达：