&gt; Backbone&#x27;s only hard dependency is Underscore.js ( &gt;= 1.7.0). For RESTful persistence and DOM manipulation with Backbone.View, include jQuery ( &gt;= 1.11.0), and json2.js for older Internet Explorer support. (Mimics of the Underscore and jQuery APIs, such as Lo-Dash and Zepto, will also tend to work, with varying degrees of compatibility.)<p>It&#x27;s not a true dependency but it&#x27;s a default companion and optional dependency (see Backbone.$).<p>Source: <a href="http:&#x2F;&#x2F;backbonejs.org" rel="nofollow">http:&#x2F;&#x2F;backbonejs.org</a>