title: What browsers currently support JavaScript's 'let' keyword?
body: <p>I'm developing an app and don't have to ever worry about Internet&nbsp;Explorer and was looking into some of the features present in A+ grade browsers that aren't in Internet&nbsp;Explorer1.</p>
  
  <p>One of these features I wanted to play around with is <a href="https://developer.mozilla.org/en/New_in_JavaScript_1.7#let_definitions" rel="noreferrer" title="New in JavaScript 1.7 - MDC">JavaScript's let keyword</a></p>
  
  <p>I can't seem to get any of their 'let' examples to work in Firefox 3.6 (<a href="https://en.wikipedia.org/wiki/User_agent#Use_in_HTTP" rel="noreferrer">User-Agent</a> string: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2) Gecko/20100115 Firefox/3.6 (.NET CLR 3.5.30729)). I get <code>SyntaxError: missing ; before statement</code> when executing <code>let foo = "bar"</code>.</p>
  
  <p>So, what browsers support the let keyword? (Or am I doing something wrong?)</p>