Question

My programing background is that I learned a little Java in school. JavaScript syntax tends to confuse me for some reason. The JavaScript code below is a pattern of syntax that I don’t know what to make of:

foo.ready = function(variable){... var whatever = variable.bar();

One of my main points of confusion is the parameter. For a contrasting example, in Java, if I call a method with one parameter, the call sends one parameter. I don’t see how the parameter named ‘variable’ is ever set.

Answer 1

The variable is assigned when foo.ready is invoked, and passed some value (presumably a function).

var foo = {};  // 1. Create an object named "foo"

  // 2. Assign a function to the "ready" property of "foo"
foo.ready = function(variable) {

       // 4. "foo.ready" has been invoked, and received a function to its
       //         "variable" parameter, which it then invokes.
       //    The return value is assigned to "whatever"
     var whatever = variable();  

     alert( whatever );   // 5. alert the value returned from the function

};

  // 3.  Invoke "foo.ready" passing a function as the argument.
  //         The function merely returns a string
foo.ready( function() { return "Hello world"; } );

Here’s a working example: http://jsfiddle.net/69grz/