The data-toggle attributes in Twitter Bootstrap

Question

It is a Bootstrap data attribute that automatically hooks up the element to the type of widget it is. Data-* is part of the html5 spec, and data-toggle is specific to Bootstrap.

Some Examples:

data-toggle="modal"
data-toggle="collapse"
data-toggle="dropdown"
data-toggle="tab"

Go through the Bootstrap JavaScript docs and search for data-toggle and you will see it used in the code examples.

One working example:

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/js/bootstrap.min.js"></script>
<link href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.6/css/bootstrap.min.css" rel="stylesheet"/>

<div class="dropdown">
  <a class="dropdown-toggle" data-toggle="dropdown" href="#">Dropdown trigger</a>
  <ul class="dropdown-menu" role="menu" aria-labelledby="dLabel">
    <li><a href="#">Item</a></li>
  </ul>
</div>

Any attribute that starts with data- is the prefix for custom attributes used for some specific purpose (that purpose depends on the application). It was added as a semantic remedy to people's heavy use of rel and other attributes for purposes other than their original intended purposes (rel was often used to hold data for things like advanced tooltips).

In the case of Bootstrap, I'm not familiar with its inner workings, but judging from the name, I'd guess it's a hook to allow toggling of the visibility or perhaps a mode of the element it's attached to (such as the collapsable side bar on Octopress.org).

html5doctor has a good article on the data- attribute.

Cycle 2 is another example of extensive use of the data- attribute.

For example, say you were creating a web application to list and display recipes. You might want your customers to be able to sort the list, display features of the recipes, and so on before they choose the recipe to open. In order to do this, you need to associate things like cooking time, primary ingredient, meal position, and so on right inside the list elements for the recipes.

<li><a href="recipe1.html">Borscht</a></li>
<li><a href="recipe2.html">Chocolate Mousse</a></li>
<li><a href="recipe3.html">Almond Radiccio Salad</a></li>
<li><a href="recipe4.html">Deviled Eggs</a></li>

In order to get that information into the page, you could do many different things. You could add comments to each LI element, you could add rel attributes to the list items, you could place all the recipes in separate folders based on time, meal, and ingredient (i.e. ). The solution that most developers took was to use class attributes to store information about the current element. This has several advantages:

• You can store multiple classes on an element
• The class names can be human readable
• It’s easy to access classes with JavaScript (className)
• The class is associated with the element it’s on

But there are some major drawbacks to this method:

• You have to remember what the classes do. If you forget or a new developer takes over the project, the classes might be removed or changed without realizing that that affects how the application runs.
• Classes are also used for styling with CSS, and you might duplicate CSS classes with data classes by mistake, ending up with strange styles on your live pages.
• It’s more difficult to add on multiple data elements. If you have multiple data elements, you need to access them in some way with your JavaScript, either by the name of the class or the position in the class list. But it’s easy to mess up.

All the other methods I suggested had these problems as well as others. But since it was the only way to quickly and easily include data, that’s what we did. HTML5 Data Attributes to the Rescue

HTML5 added a new type of attribute to any element—the custom data element (data-*). These are custom (denoted by the *) attributes that you can add to your HTML elements to define any type of data you want. They consist of two parts:

Attribute Name This is the name of the attribute. It must be at least one lowercase character and have the prefix data-. For example: data-main-ingredient, data-cooking-time, data-meal. This is the name of your data.

Attribute Vaule Like any other HTML attribute, you include the data itself in quotes separated by an equal sign. This data can be any string that is valid on a web page. For example: data-main-ingredient="chocolate".

You can then apply these data attributes to any HTML element you want. For example, you could define the information in the example list above:

<li data-main-ingredient="beets" data-cooking-time="1 hour" data-meal="dinner"><a href="recipe1.html">Borscht</a></li>
<li data-main-ingredient="chocolate" data-cooking-time="30 minutes" data-meal="dessert"><a href="recipe2.html">Chocolate Mousse</a></li>
<li data-main-ingredient="radiccio" data-cooking-time="20 minutes" data-meal="dinner"><a href="recipe1.html">Almond Radiccio Salad</a></li>
<li data-main-ingredient="eggs" data-cooking-time="15 minutes" data-meal="appetizer"><a href="recipe1.html">Deviled Eggs</a></li>

Once you have that information in your HTML, you will be able to access it with JavaScript and manipulate the page based on that data.

From the Bootstrap Docs:

<!--Activate a modal without writing JavaScript. Set data-toggle="modal" on a 
controller element, like a button, along with a data-target="#foo" or href="#foo" 
to target a specific modal to toggle.-->

<button type="button" data-toggle="modal" data-target="#myModal">Launch modal</button>

So many answers have been given, but they don't get to the point. Let's fix this.

http://www.w3schools.com/bootstrap/bootstrap_ref_js_collapse.asp

To the point

1. Any attribute starting with data- is not parsed by the HTML5 parser.
2. Bootstrap uses the data-toggle attribute to create collapse functionality.

How to use: Only 2 Steps

1. Add class="collapse" to the element #A you want to collapse.
2. Add data-target="#A" and data-toggle="collapse".

Purpose: the data-toggle attribute allows us to create a control to collapse/expand a div (block) if we use Bootstrap.