How to check if a class in javascript exists
<p>I am defining a class in javascript using this...</p>

<pre><code>// file_a.js
function class_a() {
    this.prop1 = null;
    this.prop2 = null;
}

// file_b.js
var obj = new class_a;
// I need to check here if class_a exists
</code></pre>

<p>How can I do this?</p>

<p>Regards</p>
