Anything But Typical: Learning to Love JavaScript Prototypes

Anything But Typical
Learning to Love JavaScript Prototypes
Page 1© 2010 Razorfish. All rights reserved.
Dan Nichols
March 14, 2010

JavaScript

Object-Oriented Programming

class

Inheritance

prototype(not the library)

The story so far…

…except it wasn’t all good.

Sound familiar?

prototype(not the library) to the rescue!

Everything is an object

Every object has a prototype

prototypes do good things

Encourage modularityand reusability

Provide a consistent wayto do (different) things

Keep code to a minimum

Make complexity easy

What is a prototype, exactly?

A reference point for other objects

Property lookup chain

instance
Date
Object

JavaScript is different frommost other OOP languages

Anatomy of a prototype
rex
Poodle
Dog
Object

Constructor

Property
Method

Constructor
Inheritance

Instance
Instance Property

this and the lookup chain
fluffy
socks
Cat
Object

socks
Cat
Object

fluffy
Cat
Object

Execution context: this and call()

Execution context with instances
Same outcome

Inheritance

Working with inherited behavior
LimitedContainer
Container
Object

LimitedContainer
Container
Object

JavaScript is the Frankensteinof the OOP world

Borrowing from multiple prototypes

One small problem

The constructor problem

Fixing the constructor problem

prototype isn’t love at first sight

Putting prototypes to work

Requirements
Four kinds of rules on the form:
Required
Email
Number
Zip Code
Multiple rules can apply to one field
Rules need to be inferred from data-rich, standard HTML
Error messages should be specific
Flexible enough to be:
Usable for all other forms on the site
Extended for use in other projects

The Plan
On load:
Create validation rules for each field
Set up submit handler
When form is submitted:
Cycle through all rules
If a field fails a rule
Mark it invalid
Create an error message for it
Don’t check any more rules for that field
Show all error messages

NumberValidator
EmailValidator
RequiredValidator
PatternValidator
ValidatingForm
Validator
Object

Libraries are there to make life easier

Think about your approach

Dive in!

Thank You
Dan Nichols
dan.nichols@razorfish.com
Blog: http://heydanno.com/blog
Code demo: http://heydanno.com/sxsw

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Anything But Typical: Learning to Love JavaScript Prototypes

by Razorfish on Apr 02, 2010

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Anything But Typical: Learning to Love JavaScript Prototypes — Presentation Transcript