Generic way to detect if html form is edited

Question

I have a tabbed html form. Upon navigating from one tab to the other, the current tab\'s data is persisted (on the DB) even if there is no change to the data.

I woul

Answer 1

Here's how I did it (without using jQuery).

In my case, I wanted one particular form element not to be counted, because it was the element that triggered the check and so will always have changed. The exceptional element is named 'reporting_period' and is hard-coded in the function 'hasFormChanged()'.

To test, make an element call the function "changeReportingPeriod()", which you'll probably want to name something else.

IMPORTANT: You must call setInitialValues() when the values have been set to their original values (typically at page load, but not in my case).

NOTE: I do not claim that this is an elegant solution, in fact I don't believe in elegant JavaScript solutions. My personal emphasis in JavaScript is on readability, not structural elegance (as if that were possible in JavaScript). I do not concern myself with file size at all when writing JavaScript because that's what gzip is for, and trying to write more compact JavaScript code invariably leads to intolerable problems with maintenance. I offer no apologies, express no remorse and refuse to debate it. It's JavaScript. Sorry, I had to make this clear in order to convince myself that I should bother posting. Be happy! :)

    var initial_values = new Array();

    // Gets all form elements from the entire document.
    function getAllFormElements() {
        // Return variable.
        var all_form_elements = Array();

        // The form.
        var form_activity_report = document.getElementById('form_activity_report');

        // Different types of form elements.
        var inputs = form_activity_report.getElementsByTagName('input');
        var textareas = form_activity_report.getElementsByTagName('textarea');
        var selects = form_activity_report.getElementsByTagName('select');

        // We do it this way because we want to return an Array, not a NodeList.
        var i;
        for (i = 0; i < inputs.length; i++) {
            all_form_elements.push(inputs[i]);
        }
        for (i = 0; i < textareas.length; i++) {
            all_form_elements.push(textareas[i]);
        }
        for (i = 0; i < selects.length; i++) {
            all_form_elements.push(selects[i]);
        }

        return all_form_elements;
    }

    // Sets the initial values of every form element.
    function setInitialFormValues() {
        var inputs = getAllFormElements();
        for (var i = 0; i < inputs.length; i++) {
            initial_values.push(inputs[i].value);
        }
    }

    function hasFormChanged() {
        var has_changed = false;
        var elements = getAllFormElements();

        for (var i = 0; i < elements.length; i++) {
            if (elements[i].id != 'reporting_period' && elements[i].value != initial_values[i]) {
                has_changed = true;
                break;
            }
        }

        return has_changed;
    }

    function changeReportingPeriod() {
        alert(hasFormChanged());
    }