title: JavaScript: Is it possible to pass a variable into a callback function that is assigned to a variable?
body: <p>A lot of people say that this is asked too much in the comments, which made me hesitant to ask this, but I still have not found a solution in their answers, mostly because (1) they are typically using jQuery and (2) the questions usually contain technicalities I do not understand.</p>
  
  <p>I have a function with a variable inside. The variable is assigned a function. I'm sure this concept is not exclusive to AJAX, but that is the context I am using it in, if it makes a difference.</p>
  
  <pre><code>function iClick(this)
  {
      var foo = "I would like to pass this.";
  
      ajax.onreadystatechange = function (foo) { alert(foo); }
  }
  </code></pre>
  
  <p>I want to pass a variable into the function. However, since there is no original function declaration, how do I specify parameters? Can I even do that?</p>