removeClass and addClass

These do exactly what they say they are doing.

addClass() - Adds a css class to the element calling the method.

removeClass() - Removes a css class from the element calling the method.

The parameter within the method is literally the css class name that is being added or removed.

Example:

Let's say we have the following html and css, a div with an id of box1 and a css class for a basic box.

.box {
   width: 200px;
   height: 200px;
}

<div id="box1">I am a box.</div>

We want to programmatically add a css class to it, that applies that general box styling to it. So using JQuery we can use the addClass method to add the box class to the html element.

$(document).ready(function() {
     $('#box1').addClass("box");
});

Will result in the html being rendered as:

<div id="box1" class="box">I am a box.</div>

If we wanted to remove the class we could just use the removeClass method instead.

$(document).ready(function() {
     $('#box1').removeClass("box");
});

Which results in:

<div id="box1">I am a box.</div>

Hope that helps clear things up for you.