JavaScript this.checked

Question

In JavaScript, if we write the following for example:

var c = this.checked;

What is checked here? Is it just a state

Answer 1

Assuming this refers to a DOM element which has a checked property (e.g. a checkbox or a radio button) then the checked property will either be true if the element is checked, or false if it's not. For example, given this HTML:

<input type="checkbox" id="example">

The following line of JS will return false:

var c = document.getElementById("example").checked; //False

Note that what you've written is standard JavaScript, not jQuery. If this refers to a jQuery object rather than a DOM element, checked will be undefined because the jQuery object does not have a checked property. If this is a jQuery object, you can use .prop:

var c = this.prop("checked");

Answer 2

To use the pseudo selector :checked with the jquery object this write:

$(this).is(':checked')

Answer 3

In jQuery checked is a selector:

The :checked selector works for checkboxes and radio buttons.

There are some ways to check if a checkbox is checked or not:

For Example:

$('#checkBox').attr('checked'); 

or 

$('#checkBox').is(':checked'); 

Answer 4

Is it just a state that tells us if a checkbox for example is checked or not? So, can we use it to check that the checkbox is also not checked?

Yes and yes