Writing a checkbox with jQuery

Why not do something like this:

$(document).ready(function() {
     $('.containerClass-filter-expression-that-selects-all-your-chks').click(function() {
       recalculate();
     });
});

function recalculate(){
   $('.some-expression-that-selects-all-your-checkboxes').each(function() {
       if($(this).is('checked')) {
           //add

       } else {
           //substract from total
       }

   });
};

I'm assuming you have an interface with multiple check boxes, and some indicator of the number currently checked... I do this all the time. There's an important thing you need to keep in mind - you can't do this by responding to click events of the checkbox, IF you have other ways that it can be checked, such as by a script, or if the checkbox might be rendered checked when the page loads. So, I create a counting function, and I call that whenever anything happens. When my script updates the boxes, I call the function. When the page loads, I call the function. I also add the function as the click event responder on all checkboxes, including my "check all" box. The function is very simple...

All my checkboxes have the class "gridCheckbox" and the function counts those, if they are checked, and puts the result into the label "lblNumSelected"...

function UpdateCheckCount() {
    $("#lblNumSelected").html("(" + $(".gridCheckbox:checked").length + ")");
}

Your code shows a misunderstanding of JQuery and what it's for. It is a Query Language over the DOM. As such, you should try to apply "group logic" whenever possible, and NEVER iterate over individual items. So, rather than writing code for each check box, you write code for ALL checkboxes at the same time. You should operate on groups (query result sets) rather than individual items, as much as possible.

You can list multiple dom selectors separated by commas, for example:

$('#tcbx1, #tcbx2, #tcbx3').click(function(){
        tblcheckboxes();
});

And since the anonymous function simply calls another function, you can just pass in the function directly:

$('#tcbx1, #tcbx2, #tcbx3').click(tblcheckboxes);

As for this part:

if ($('#tcbx1').is(":checked")) {
     a = parseFloat($("#tcbx1").val(), 10);
}
if ($('#tcbx2').is(":checked")) {
     b = parseFloat($("#tcbx2").val(), 10);
}

This is trickier, because although the operations inside are very similar, you are assigning to different variables. A workaround could be to assign to array elements instead of a, b, c, where the right element index could be extracted from the number in the #tcbxN id. Then you could use a loop, creating id names as "#tcbx" + i and using the loop variable i to assign values into the array. But that still wouldn't be great.

To be honest, this code with variable names like a, b, c look quite hypothetical. If you presented a real life problem with well-named variables, we might be able to provide better big-picture suggestions to shorten the code.

I tried some of the answers,did not work for me. I played around a bit on JSFiddle, to come up with the below code. Your JQuery selector can change as per the structure of the HTML page. Also,note it's is(':checked')

var count=0;
    $("input[type='checkbox']").on('click',function(e){
        if($(this).is(':checked'))
           count+= parseInt($(this).val());
        else
            count-= parseInt($(this).val());
        console.log(count)
    });

Src : http://jsfiddle.net/sahiljambhekar/8498q9ox/2/

If there are no other checkboxes on the page, just select all checkboxes using $('[type="checkbox"]'). If you can't select all checkboxes, put a class on your checkboxes and select the class by using $('.theCheckboxClass'). If you are a sadist, select all your checkboxes by id e.g. $('#tcbx1, #tcbx2, #tcbx3'). We'll use the checkbox element selector for simplicity. Bind the function to calculate totals to the change event instead of click.

var checkBoxes = $('[type="checkbox"]');
checkBoxes.change(function () {
    var total = 0;
    checkBoxes.filter(":checked").each(function() {
        total += parseFloat($(this).val(), 10);
    });
    DoSomethingWithTotal(total);
});