Tag: web programming

Changing checkbox value when (un)checked

This bit of code handles another rather esoteric scenario — I have a generic “go to this URL and download the resultant Excel file” JavaScript function. This is because I write a lot of reporting tools and didn’t want to write a lot of code for each new tool. The template is an input form with a submit button that calls the generic function. Params for the elements on the form from which values are read, the URL to call to generate the report, and the POST elements into which each corresponding form value is inserted gets stuffed. Works great for text inputs. Works fine for drop-downs. But the value of a checkbox is really a combination of the potential value (from the value tag) and the checked state. That is — my Button 1 has a potential value of 1, but if the box is checked or not is really important.

Instead of attempting to determine the type of element in each form input so I can evaluate the checked condition, I decided to just change the value when the checkbox state is changed. Now Button 1 has a potential value of 0 when unchecked and a potential value of 1 when checked. I don’t need to know if the box is checked because the value answers that question. So passing along button1’s value to my URL lets the target site know if I want whatever Button 1 represents. (In this case, users are able to select from a list of seven data sources — smaller numbers of data sources reduce the query time but also fail to provide the most robust report).

The JavaScript to handle changing the checkbox value when the checked state changes:

$("#button1").change(function () {
    if ($("#button1").is(':checked')) {
        $("#button1").val(1);
    }
    else{
        $("#button1").val(0);
    }
});

$("#button2").change(function () {
    if ($("#button2").is(':checked')) {
        $("#button2").val(1);
    }
    else{
        $("#button2").val(0);
    }
});

The HTML defining these two checkboxes:

<input type="checkbox" id="button1" name="button1" value="1" checked><label for="ngmss">Thing 1</label>
<input type="checkbox" id="button2" name="button2" value="1" checked><label for="ngmss">Thing 2</label>

HTML Checkbox Adding and Removing Table Row

Here’s the JavaScript code I ended up using to add and remove rows from a table based on a checkbox selection (and only allowing one checkbox per group to be selected). The biggest change is that I added a name and ID to my TR for easier identification. 

$(document).on("change", "input[type='checkbox']", function () {
    var $objCheckbox = $(this);
    if ($objCheckbox.is(":checked")) {			// When checked, deactivate other checkboxes and add to sets to create table
        var objCheckboxGroup = "input:checkbox[tableselector='" + $objCheckbox.attr("tableselector") + "']";

        $(objCheckboxGroup).prop("disabled", true);
        $objCheckbox.prop("disabled", false);		// Allow checked box to be unchecked

        addSetToCreatingTable($objCheckbox.attr("setname"), $objCheckbox.attr("settype"), $objCheckbox.attr("goodcircuits") + "|" + $objCheckbox.attr("value"), $objCheckbox.attr("tableselector"));

    }
    else {							// When unchecked, active checkboxes and remove from sets to create table
        var objCheckboxGroup = "input:checkbox[name='" + $objCheckbox.attr("name") + "']";
        $(objCheckboxGroup).prop("disabled", false);	

        $("#" + $objCheckbox.attr('tableselector')).each(function(){ $(this).remove();})
}
});

HTML Checkboxes To Add and Remove Values from Table

I am creating a web form where the user input sometimes cannot be resolved to a unique value. In those cases, I present the user a set of checkboxes with the options (yes, a radio button makes more sense because you can only select one. But I hate that radio buttons change selection when you hit an arrow key.).

When a selection is made, I need to (1) deactivate the checkboxes for the other options when a checkbox in the group is selected and (2) add information to a data table that is used in subsequent activities.

When a selection is cleared, I need to (1) activate the checkboxes within the group and (2) remove the right row from the data table.

Below is the HTML code that achieves this. Now I just need to map this test page into the actual web code. There’s a post with the actual code I ended up using in production too.

<html>
<head><title>Adding And Removing From Table</title></head>
<body>

<div name="divCircuitClarifications" id="divCircuitClarifications">
  <h3>My-Sample-Circuit-A</h3>
    <input type="checkbox" value="123" tableselector="SampleCircuitA" name="SampleCircuitA[]" /><label>123</label>
    <input type="checkbox" value="234" tableselector="SampleCircuitA" name="SampleCircuitA[]" /><label>234</label>
    <input type="checkbox" value="345" tableselector="SampleCircuitA" name="SampleCircuitA[]" /><label>345</label>
<P>
  <h3>My-Sample-Circuit-B</h3>
    <input type="checkbox" value="abc" tableselector="SampleCircuitB" name="SampleCircuitB[]" /><label>abc</label>
    <input type="checkbox" value="bcd" tableselector="SampleCircuitB" name="SampleCircuitB[]" /><label>bcd</label>
    <input type="checkbox" value="cde" tableselector="SampleCircuitB" name="SampleCircuitB[]" /><label>cde</label>
<P>
  <h3>My-Sample-Circuit-C</h3>
    <input type="checkbox" value="Cabc" tableselector="SampleCircuitC" name="SampleCircuitC[]" /><label>abc</label>
    <input type="checkbox" value="Cbcd" tableselector="SampleCircuitC" name="SampleCircuitC[]" /><label>bcd</label>
    <input type="checkbox" value="Ccde" tableselector="SampleCircuitC" name="SampleCircuitC[]" /><label>cde</label>
<P>
</div>

<div id="divResultTable" name="divResultTable">
<table border="1" padding="1" name="tableSetsToCreate" id="tableSetsToCreate">
	<thead><tr><th>ECCKT</th><th>Circuit ID</th></tr></thead>
	<tbody></tbody>
</table>


<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.1/jquery.min.js"></script>

<script>
	$("input:checkbox").on('click', function() {
	  	var $objCheckbox = $(this);
	  	if ($objCheckbox.is(":checked")) {			// When checked, deactivate other checkboxes and add to sets to create table
	    		var objCheckboxGroup = "input:checkbox[tableselector='" + $objCheckbox.attr("tableselector") + "']";
	
	    		$(objCheckboxGroup).prop("disabled", true);
	    		$objCheckbox.prop("disabled", false);		// Allow checked box to be unchecked

	                var strTableRowString = '<tr><td>' + $objCheckbox.attr("tableselector") + '</td><td>' + $objCheckbox.val() + '</td>\n';
	                $('#tableSetsToCreate tbody').append(strTableRowString);
	  	}
		else {							// When unchecked, active checkboxes and remove from sets to create table
	    		var objCheckboxGroup = "input:checkbox[name='" + $objCheckbox.attr("name") + "']";
	    		$(objCheckboxGroup).prop("disabled", false);	

			$("tr:contains('" + $objCheckbox.attr('tableselector') + "')").each(function(){ $(this).remove();})
  		}
	});
</script>
</body>

Inspecting An Element

In Firefox’s developer tools — instead of attempting to navigate through the HTML code to find the element, just right-click on it and select “Inspect Element”

You’ll get dropped into the Inspector tab right where you need to be.

There’s also an element picker tool that you can use instead — click on it & then click on the element within the page. Same result.