How can I shift-select multiple checkboxes like GMail?

In GMail, the user can click on one checkbox in the email list, hold down the Shift key, and select a second checkbox. The JavaScript will then select/unselect the checkboxes that are between the two checboxes.

I am curious as to how this is done? Is this JQuery or some basic (or complex) JavaScript?

I wrote a self-contained demo that uses jquery:

$(document).ready(function() {
    var $chkboxes = $('.chkbox');
    var lastChecked = null;

    $chkboxes.click(function(e) {
        if (!lastChecked) {
            lastChecked = this;
            return;
        }

        if (e.shiftKey) {
            var start = $chkboxes.index(this);
            var end = $chkboxes.index(lastChecked);

            $chkboxes.slice(Math.min(start,end), Math.max(start,end)+ 1).prop('checked', lastChecked.checked);
        }

        lastChecked = this;
    });
});

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<html>
<head>
</head>
<body>
    <input type="checkbox" id="id_chk1" class="chkbox" value="1" />Check 1<br/>
    <input type="checkbox" id="id_chk2" class="chkbox" value="2" />Check 2<br/>
    <input type="checkbox" id="id_chk3" class="chkbox" value="3" />Check 3<br/>
    <input type="checkbox" id="id_chk4" class="chkbox" value="4" />Check 4<br/>
    <input type="checkbox" id="id_chk5" class="chkbox" value="5" />Check 5<br/>
    <input type="checkbox" id="id_chk6" class="chkbox" value="6" />Check 6<br/>
    <input type="checkbox" id="id_chk7" class="chkbox" value="7" />Check 7<br/>
</body>
</html>

This is done through fairly simple javascript.

They keep track of the id of the last checked box and when when another checkbox is checked they use the shiftKey event attribute to see if shift was held while clicking the checkbox. If so they set the checked property of each checkbox in between the two to true.

To determine when a box is checked they probably use an onclick event on the checkboxes

Recently, I wrote a jQuery plugin that provide that feature and more.

After including the plugin you just need to initialize the context of checkboxes with the following code snippet:

$('#table4').checkboxes({ range: true });

Here is the link to the documentation, demo & download: http://rmariuzzo.github.io/checkboxes.js/

How can I shift-select multiple checkboxes like GMail?

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