simple js dynamically reading form values - js fails - why?

Discussion in 'Javascript' started by Randell D., Nov 24, 2003.

  1. Randell D.

    Randell D. Guest


    I am determined to stick with this... I'm getting there... for those who
    haven't read my earlier posts, I'm createing what should be a simple
    function that I can call to check that required fields in a form have
    values. I'm writing the values to the client using document.write only so
    that I can confirm that the values are there to be played with - this is not
    the final result so please (unless it's leading to the script failure)
    please ignore layout - I don't need to hear about the <br> or CSS or
    anything else that looks nice - I'm working on basic program flow at the
    moment.... Oh! and note I'm a javascript newbie comming - I have some
    progarmming experience with PHP which I would have thought would have helped
    me along a bit...

    So... Can someone help my next step? In my script below, it draws a basic
    form - The theory behind it is once values have been written in to the two
    form fields and the user presses the submit button, I would expect to have
    the form values re-gurgitated (?) back on to the screen (again, just to
    prove that the values are visable inside firstFunction()

    I want the script to be dynamic - Thus, from an onclick event on the submit
    button, the function is called and passed the form name, a required form
    field (as named inside the "<INPUT>" html tag), followed by the 'real name'
    of the tag that the user gets to see in the browser. Thus... the idea being
    that if the input tag 'firstname' has no value, an alert box will popup
    asking for a value for "First Name" and not "firstname'.

    My problem?

    If you examine the script, variable xyz gets assigned the firstname entered
    in the form - This is proven (ie displayed using document.write).

    The next step is to create a loop that would read the supplied arguements to
    read values from the form. Thus... my example would be form fields
    'firstname' and 'lastname'...

    What is done are the arguements passed to the function are displayed (these
    are the form field tag names). And when I try to use these values (see
    variable tmpe in the script) to display form field values, the script
    exits - no errors - nothing. When I exclude 'tmpe' from the script, the
    script completes by looping twice (since the function was passed two field
    names)... but I cannot use the form field names dynamically within the
    loop... why?

    All help, via the newsgroup (share+help others) is much appreciated, thanks

    My script (also at

    <script type="text/javascript">
    function firstFunction(formName)
    // Read in arguements passed to the function from the onClick event in the
    forms submit button
    var argv = firstFunction.arguments;
    var argc = firstFunction.arguments.length;
    // The document.write below *did* work earlier - Now the script exits when I
    include it - why?
    // document.write("argc = " + argc);

    // Can we read anything from the form? Try a hard code reading of a form
    var xyz=document.forms[formName].elements['firstname'].value;
    document.write(" xyz = " + xyz);

    // Simplify our form data object name in to formData
    var formData=document.forms[formName];

    // Define tmpe - for our test purposes, we assign a dash as a value just so
    that we know
    // it has a value
    var tmpe="-";

    // Loop through the numbre of arguements passed to firstFunction() - Read
    from the second arguement
    // since the first arguement is formName
    for(count=1; count<argc; count=count+2)
    { // Simplify our form field name in to a single variable
    // Again, for the hell of it, confirm fieldName is valid by making
    note of its length
    // tmpc is the user friendly name of a field - thus it has a value of
    First Name as opposed
    // to the html tag name firstname
    // Dump our values to the screen, one per line to make things easier
    to read.
    document.write("<hr>count=" + count + "<hr>fieldName=" + fieldName
    + "<hr>tmpb=" + tmpb + "<hr>tmpc = " + tmpc );

    // I have tried the following methods to define a value for tmpe but
    they fail -
    // What is the correct syntax and if possible, why does it fail?
    // tmpe=formData.elements[fieldName].value;
    // tmpe=document.forms[formName].elements[fieldName].value;
    // tmpe=document.forms[formName].elements['firstname'].value;
    document.write("<hr>tmpe=" + tmpe);
    // Brace below closes the for loop

    // Brace below closes the function


    <form name="myForm">
    <br>Firstname: <input type=text name=firstname size=30> Lastname: <input
    type=text name=lastname size=30>
    <input type="submit" onclick="firstFunction('myForm','lastname','Last
    Name','firstname','First Name'); return">
    <hr><a href="./e.html">again</a><hr>

    Randell D., Nov 24, 2003
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  2. Randell D.

    Randell D. Guest

    "Randell D." <> wrote in message

    I got it... in a previous post I had been told not to use document.write and
    use alert() instead - I was told that using document.write was ineffiicient
    but I had not realised that it was causing my problems...

    I've written my scrpit exactly the way I'd like it to work - thanks to all
    who helped...
    Randell D., Nov 25, 2003
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