Did anyone else do a double take reading this?

> If you’re a JavaScript programmer, chances are you’ve seen (and done) something like this before:

    var listener = node.addEventListener("click", function(event) {
        let _target = event.target;
        this.handleClick(_target);
    }.bind(this));

I had to go look up `let` in JavaScript[1]. It appears to still be a bleeding-edge feature not widely supported[2] outside of Firefox... not even in Node with the --harmony flag. I wonder if this is meant to be subtle pro-ES6 propaganda, or the author really takes `let` for granted and doesn't realize most JS programmers have never seen it :)

1. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Refe...

2. http://kangax.github.io/es5-compat-table/es6/#let