It was very undivided 8 years ago - it was common knowledge to never, ever override the prototypes of built-in objects.  In fact, a major reason that JQuery won out over Prototype &amp; Mootools was because the latter two monkey-patched built-in prototypes, and as a result were incompatible with each other or with any other library that overrode built-in methods.<p>IIRC, this was an interview question at Google when I applied in 2008, and I think one of the reasons I got the job was because I was aware of all of the pitfalls of it.<p>I managed to skip using underscore, but from a quick glance through the library, isn&#x27;t the reason it&#x27;s called <i>underscore</i> because it provides &#x27;_&#x27; as a namespace for all the utility functions, rather than altering Array.prototype the way Prototype did?