Source: JavaScript Enlightenment


If you are a designer or developer who has only used JavaScript under the mantle of libraries (such as jQuery, MooTools, Zepto, YUI, Dojo, etc.), it is my hope that the material in this book will transform you from a JavaScript library user into a JavaScript developer.

What exactly do you think this expression means?

  • That you've been relying on library code to help you code, and now you will be able either to forgo the use of libraries or to code libraries yourself. You will tinker "under the hood" yourself, with no library functions to help you along. Dec 5, 2015 at 17:16

1 Answer 1


A "mantle" is a "cloak". This quotation is stretching the meaning of "cloak" to the more general "cover". So this part of the sentence means "libraries like Zepto use JavaScript under the covers".

The phrase "under the covers" is being used metaphorically. There are two common literal meanings of "under the covers":

  • The insides of a piece of machinery, which are covered by a removable "hood" or "cover". A closed hood makes it harder for the user to accidentally hurt themselves or damage the machine.
  • Being in bed, under sheets and/or blankets. Sheets and blankets are layers of "covers".

In computer programming, the purpose of a "programming library" is to provide easy-to use features, without the user needing to worry about the details of how the features are implemented. This also avoids bugs: If the user never works with the details, the user cannot make a mistake by mis-using the details. These "hidden details" are "under the covers".

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