Question

I’m trying to write some JavaScript for my website that will select all the forms on a page, add an event listener for when they are submitted, and then route the values submitted to the main action page and an additional alternate page.

Here’s what I have so far:

Send.php:

<script type="text/javascript">


    function post_to_url(path, params, method) {
        method = method || "post"; // Set method to post by default, if not specified.

        // The rest of this code assumes you are not using a library.
        // It can be made less wordy if you use one.
        var form = document.createElement("form");
        form.setAttribute("method", method);
        form.setAttribute("action", path);

        for(var key in params) {
            var hiddenField = document.createElement("input");
            hiddenField.setAttribute("type", "hidden");
            hiddenField.setAttribute("name", key);
            hiddenField.setAttribute("value", params[key]);

            form.appendChild(hiddenField);
        }

        document.body.appendChild(form);    // Not entirely sure if this is necessary
        form.submit();
    }

    function addEvent(elm, evType, fn, useCapture) {
        if (elm.addEventListener) {
            elm.addEventListener(evType, fn, useCapture);
            return true;
        }
        else if (elm.attachEvent) {
            var r = elm.attachEvent('on' + evType, fn);
            return r;
        }
        else {
            elm['on' + evType] = fn;
        }
    }

    function addLoadEvent(func) {
        var oldonload = window.onload;
        if (typeof window.onload != 'function') {
            window.onload = func;
        }
        else {
            window.onload = function() {
                oldonload();
                func();
            }
        }
    }

    function addSubmits() {
        var fs=document.forms;
        for(var i=0;i<fs.length;i++){
            //addEvent(fs[i],"submit",post_to_url('http://www.gwtwg.com/recieve.php', {'email' : 'test.com'}), false)
        }
    }

    addLoadEvent(addSubmits);
</script>

<form method="post" action="<?php echo $_SERVER["PHP_SELF"]; ?>">
    <input type="text" name="email" />
    <input type="submit" value="Submit!" />
</form>

Right now the script just freezes up, but if I replace: “post_to_url(‘http://www.gwtwg.com/recieve.php‘, {’email’ : ‘test.com’})”
with:
“alert(“foobar”)”

I get an alert when I load the page and when the form is submitted. (It should only occur when the button is submitted).

Any thoughts on whats wrong?

Answer 1

So, the problem here is really that you’re not using any JS library. Personally I would recommend that you use jQuery, but any of the major ones will work. All of the functions you showed have more robust equivalents in the various JS libraries, so it’s silly to try and debug them when you can just replace them with better-tested, more robust versions, for free.

If you were using jQuery, here’s how (I think) you could do what you want to do:

var URL = "http://www.gwtwg.com/recieve.php"; // Define your site's URL
$(function() { // setup an onReady (similar to onLoad) handler
    $("form") // get all forms on the page
        .submit(function() { // hook up an onSubmit handler to them
            var params = $(this).serialize(); // get this form's data
            $.post(URL, paprams);// POST the data your server
      });
});

Now, I haven’t actually tested any of that, but it should work (and even if it doesn’t, hopefully you get the idea). Also, notice how much shorter it is? Yet another benefit. The important thing though is, if you use established code, that’s been reviewed by hundreds of eyeballs, you won’t spend time re-inventing the wheel. Also, far more importantly, you won’t waste time begging people on the Internet to help you debug your version of that wheel 😉