How to avoid duplicated code in JavaScript / jQuery?

Question

First, a little disclaimer: I'm no master at working with javaScript / jQuery, although I have handled it quite a few times. Recently, I have sometimes found myself being forced to make redundant code, i.e. repeat line(s) of code regarding diferent events, because I don't know how to do it in a more efficient way. A small example would be enabling a button after checking if any checkbox in a page is selected. This is done either upon page loading or after any checkbox is selected:

var checkboxes = $("input[type='checkbox']");

$('#nextfl').attr("disabled", !checkboxes.is(":checked"));

checkboxes.click(function()
{
    $('#nextfl').attr("disabled", !checkboxes.is(":checked"));
});

I don't think this could be solved using the bind or on functions, for instance, since it refers to events not related to the same element. I believe it must exist a straightforward solution to this though, but as I said before, I have little experience in JS / jQ, and there are some similar situations where I have repeated dozens of lines of code, which is of course at least a bad practice.

Jonathan Michalik · Accepted Answer · 2015-07-11 16:11:15Z

1

You can always split redundant code into functions with javascript:

function doCheckboxLogic () {
    $('#nextfl').attr("disabled", !checkboxes.is(":checked"));
    // and any other logic that needs to be done
}

You then call that function in place of the redundant code block:

checkboxes.click(function()
{
    doCheckboxLogic();
});

There's not much gained here since it's one line of code anyway, but this really helps with encapsulating more complicated blocks of logic

answered Jul 11, 2015 at 16:11

Jonathan Michalik

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Rory McCrossan · Accepted Answer · 2015-07-11 16:12:35Z

1

Best practice in this case is to extract common logic to its own function which can be called as required. Try this:

$(function() {
    var $checkboxes = $("input[type='checkbox']");

    function checkState() {
        $('#nextfl').attr("disabled", !$checkboxes.is(":checked"));
    }

    $checkboxes.click(checkState); // run the function on click of a checkbox
    checkState(); // run it on load of the page
});

answered Jul 11, 2015 at 16:12

Rory McCrossan

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