Understanding prototype method calls

Question

In trying to call a method on the CodeMirror javascript code editor. I'm new to javascript and trying to understand how object oriented stuff works. I'm having problems calling what I believe are methods. For instance,

var editor = CodeMirror.fromTextArea('code', options);
editor.grabKeys(function(e) { alert("Key event");});

This gives the Uncaught TypeError: Cannot call method 'grabKeys' of undefined. Looking at the editor object reveals that grabKeys seems to be located at editor.__proto__.grabKeys.

How should I be thinking about this?

Answer 1

Probably yoour code should be something like this:

var editor = new CodeMirror.fromTextArea('code', options);
editor.grabKeys(function(e) { alert("Key event");});

Notice the 'new' operator..

Here is a good explanation of what prototype method calls are for:

http://www.javascriptkit.com/javatutors/proto.shtml