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What is the best and cross-browser way to know in javascript that Bootstrap 3 has already added on the page?

Argnist
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2 Answers2

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One potential way is to simply check for the presence of the various Bootstrap plugins you're utilizing. For example: 

if(typeof $.fn.modal === 'function') {
  //it's on the page
}

All jQuery plugins are added to the jQuery prototype and their existence can be checked on the jQuery.fn property. See How can I check if a jQuery plugin is loaded?

More simply, you could just do: 

if($.fn.modal) {
  //it's on the page
}

Looking at Bootstrap's JS source, it doesn't seem to drop any globals that you could check for.

Community
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ccnokes
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This is not the best answer - bootstrap.js adds a lot of extensions to the jQuery - things like $.fn.button. If you are using standard bootstrap package you can check as follows:

if (typeof $.fn.button === 'function' && typeof $.fn.button.Constructor === 'function') {
    // $.fn.button.Constructor.VERSION contains current version 
}

If you don't use bootstrap.js at all or you use custom version of the bootstrap library then this way may not work.

Boris Tyumnev
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