title: What is "strict mode" and how is it used?
body: <p>I've been looking over the JavaScript reference on the <a href="https://en.wikipedia.org/wiki/MDN_Web_Docs" rel="noreferrer">Mozilla Developer Network</a>, and I came across something called <code>&quot;strict mode&quot;</code>. I read it over and I'm having trouble understanding what it does. Can someone briefly explain (in general) what its purpose is and how it is useful?</p>