<!DOCTYPE html>
<html lang="en">
    <head>
        <meta charset="UTF-8">
    </head>
    <body>

        <script>
             const _searchStrIndexOf = (str, target) => {

                let index = -1;
                let len = target.length;
                let sum = 0;
                do{
                    index = str.indexOf(target,index+len);
                    sum++;
                }while(index != -1)
            	    sum--;
                    return sum;
             }
        </script>
    </body>
</html>