title: jQuery.each() -- how does jQuery know whether argument is index, key, value or object?
body: <p>Say something like this:</p>
  
  <pre><code>$.each(json_object_or_array, function(arg1, arg2) {
  
        //do something
  });
  </code></pre>
  
  <p>I've seen cases where <code>arg1</code> , <code>arg2</code> are <code>i</code> or <code>index</code> or <code>key</code> or <code>val</code> or <code>value</code> or <code>obj</code> or even random names that are implicitly referring to one of these. For example, I've seen <code>function(key, val)</code> also presented as <code>function(name, val)</code>. How does jQuery know that <code>name</code> here is referring to <code>key</code>?</p>
  
  <p>How does jQuery know what we're referring to?</p>