js判断字符串str是否包含字符串substr

js判断字符串str是否包含字符串substr:

function addUser(id,realName){
        var userids = $("#userids").val();

        if (userids!=""&&userids!=null) {
            if (!isContains(userids,id)) {
                userids = userids + id + ",";
            }
        }else{
            userids = id + ",";
        }
        $("#userids").val(userids);

        var realnames = $("#realnames").val();
        if (realnames!=""&&realnames!=null) {
            if (!isContains(realnames,realName)) {
                realnames = realnames + realName + ",";
            }

        }else{
            realnames = realName + ",";
        }
        $("#realnames").val(realnames);

    }
　　 //判断str中是否包含substr
    function isContains(str, substr) {
        return str.indexOf(substr) >= 0;
    }