title: NodeJS TypeError Callback is not a function
body: <p>I have the following piece of code:</p>
  
  <pre><code>function fun1(callback){
    var result =  "result of function 1";
    callback(result)
  };
  function fun2(callback){
    var result =  "result of function 2";
    callback(result)
  };
  
  fun1(log); // displays "result of function 1"
  fun2(log); // displays "result of function 2"
  fun2(fun1(log)); // Type Error ...
  </code></pre>
  
  <p>Where log is simple function (i.e. console.log(data)...)
  I'm wondering why fun2(fun1(log)) does not display "result of function 1" as one would expect. What is missing? Many thanks - Christian</p>