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  1. #1
    New to the CF scene
    Join Date
    Oct 2012
    Arizona, USA
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    Smile How do I use Javascript to mask a field?

    I have two fields, date field and a phone field, I would like to put a mask on. On my html my language=VB. I have been told I need to use Javascript to do this. Can you tell me if I can switch to Javascript in the middle of my html? If so how do I code the Javascript for these two fields?


  2. #2
    Supreme Master coder! Philip M's Avatar
    Join Date
    Jun 2002
    London, England
    Thanked 2,699 Times in 2,675 Posts
    The weakness of an input mask for a phone number is that it allows paste. (although that can be overcome)

    Phone Number: <input type="text" name="phone" id = "phone" length = "10" maxlength = "10" onkeypress='return inputMask(event,"1234567890")'>
    <script type = "text/javascript">
    function inputMask(e,charsAllowed) {
    //validates textbox input against allowed characters
    if (charsAllowed.indexOf(String.fromCharCode(e.keyCode)) == -1) {
    return false;
    Another way is to validate the phone number onblur:-

    PHONE: <input type = "text" name = "myphone" id = "myphone" length = "10" maxlength = "10"  onblur="checkphone()">
    <script type = "text/javascript">
    function checkphone() {
    var f = document.getElementById("myphone").value;
    if (!/^(\d{10})$/.test(f)) {
    alert ("Please fill a 10-digit phone number");
    document.getElementById("myphone").value= "";
    return false;
    Another way is to use three input boxes:-

    Phone Number <input type = "text" id = "Ph1" size =" 3" maxlength = "3" onkeyup = "validate(this,2)">
    <input type = "text" id = "Ph2" size =" 3" maxlength = "3" onkeyup = "validate(this,3)">
    <input type = "text" id = "Ph3" size =" 4" maxlength = "4" onkeyup = "validate(this,3)">
    <script type = "text/javascript">
    function validate(which,next) {
    var val = which.value;
    val = val.replace(/[^0-9]/g,"");
    which.value = val;
    next = "Ph" + next;
    if (val.length == 3){

    Dates can be dealt with in a similar manner. Remember that validating a date format does not ensure that the date is valid (e.g. 31st February).

    Scripts should be placed in the HTML right in front of the closing </body> tag.

    See also http://whattheheadsaid.com/2011/11/j...o-we-need-them

    “If you only do what you know you can do - then you never do very much.” - Tom Krause
    Last edited by Philip M; 10-16-2012 at 06:01 PM.

    All the code given in this post has been tested and is intended to address the question asked.
    Unless stated otherwise it is not just a demonstration.


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