<!DOCTYPE html>
<html>
<body>
<p id="p1">1 2 3 1 1 1 1 1 1 1 </p>
<button onclick="myFunction()">Try it</button>
<p id="demo"></p>
<script>
function myFunction() {
var str = document.getElementById("p1").innerHTML;
var pom=0;
var pos = str.indexOf("1");
document.getElementById("demo").innerHTML = pos;
/ for(let m=0;m<str.length;i++)
{
{ if（pos==1）
{
pom=pom+1;
}
}
}
</script>
</body>
</html>
