HTML Form text checked with javascript regular expression

Question

I work on an html form, which I need checked with javascript regex but it is only working if I put in static text. I need the html form text(input data) to be checked against the regex.

I have searched for this around, but i can only find people showing examples with static text.

Fruther explanation: I don't need help for understanding the regular expressions. I need to understand how to pass the data, which the user inputs - into the check against the regular expression.

    <script>
    function fn() {
    var x=document.getElementById("fname");
    xv=x.value.toUpperCase();

    var re = new RegExp("s", "g"); //Here is the expression i am searching for - This i do understand// 
    var result = re.test( ?? ); //Here should go the user input from ((("fname" - var x)))

    if (result == true) {
    var result = $("#result").empty();
    $.post('../search.php',{xv : xv},
    function(data){
    result.append(data);
    }

    if (result == false) {  
    var result = $("#result").empty();
    result.append("try again");
    }
    }
    </script>

Answer 1

Do you mean:

    var re = new RegExp("s", "g");
  **var result = re.test(xv);**
    if (result == true) {

    }

    if (result == false) {  

    }