title: String replace with a third argument mysteriously working
body: <p>I've stumbled upon some unexpected behavior from some code.</p>
  
  <pre><code>var c = "\"a\", \"b\", \"c\"";
  c.replace(/"|\s/g, "")
  </code></pre>
  
  <p>This outputs the string "a,b,c" as expected.</p>
  
  <p>Later in the code I found</p>
  
  <pre><code>var c = "\"a\", \"b\", \"c\"";
  c.replace(/"|\s/g, "", "")
  </code></pre>
  
  <p>This also outputs the string "a,b,c" without any errors but I can't find in any documentation String.prototype.replace() taking 3 arguments. The string on the last argument doesn't seem to make any difference whatever it is. What is going on? What am I missing?</p>