title: What does = +_ mean in JavaScript
body: <p>I was wondering what the <strong>= +_</strong> operator means in JavaScript.  It looks like it does assignments.</p>
  
  <p>Example:</p>
  
  <pre><code>hexbin.radius = function(_) {
     if (!arguments.length)
         return r;
     r = +_;
     dx = r * 2 * Math.sin(Math.PI / 3);
     dy = r * 1.5;
     return hexbin;
  };
  </code></pre>