May 2010 Meetup Minutes
By Ken Snyder, published 2010-05-07
Ken Snyder presented at the May 6th meeting on “Inheritance, Event Delegation and Named Function Expressions”Named Function Expressions
Kangax has a great writeup exploring function declarations and function expressions: http://yura.thinkweb2.com/named-function-expressions/ . There are a few main differences:
- Declarations are in the form `function name() {}`. Expressions are part of a code expression such as assignment: `var name = function name() {}`
- Declarations are parsed immediately so the functions can be run before declared; they are parsed even if in closures or conditional statements. Expressions are parsed when encountered.
- Declarations are useless unless named. Expression functions can be unnamed and will show up in stack traces as `?` or `anonymous`; when named, the name is only defined within the function itself (except incorrectly in IE).
Prototypal Inheritance
Prototypal Inhertance is different than classical inheritance. Functions are king and inheritance is performed by setting the prototype property of a child class to a new instance of the parent class. See http://phrogz.net/js/classes/OOPinJS2.html and http://pulpjs.org/examples/#cls .
Event Delegation
In the JavaScript Document Object Model, events bubble up to parent elements. See http://utahjs.kendsnyder.com/delegate/ and the source code. The advantages include the following:
- When child content is changed (e.g. via AJAX), the event handlers do not need to be re-attached
- CSS selector engines can be used to call different handlers for different child elements
- There are fewer event handlers
