title: Effect of x = +x in JavaScript
body: <p>Going though the <a href="http://asmjs.org/spec/latest/">asm.js</a> documentation I've observed this strange (to me at least, quite new to JS) snippet all over the sample code:</p>
  
  <pre><code>function test(x) {
      x = +x; // THIS
      ...
      return +(x*y);
  }
  </code></pre>
  
  <p>What is the purpose of the <code>+</code> on the first line?</p>