A look at the data types and how functions are invoked in JavaScript

1. JavaScript 101
André Odendaal

2. Background
Netscape Navigator
Designed by Brendon Eich in 1995
Built to replace Java for the web and be “easy to use”
Principles from Java (syntax), Self (prototypes) & Scheme (functional)
Rushed to market with good, bad & questionable design choices
Microsoft created Jscript, a compatible dialect to avoid trademark issues
ECMA
Standardized by ECMA (European Computer Manufacturers Association)
Called ECMAScript between Netscape & Microsoft
Latest version 5 includes “strict mode” for more thorough error checking

3. Basic Types
number
Only 64-bit floating point
No integers, longs, doubles, signed or unsigned to complicate matters
Associative Law does not hold for some values
(a + b) + c === a + (b + c)
string
0 or more 16-bit Unicode (UCS-2) characters. No character type
boolean
true & false

4. Objects
Object Literals
Dynamic (not based on pre-defined class) collection of properties
Property names must be a unique string within the object
Basic Operations – Get, Set & Delete
object.name | object[name]
object.name = value | object[name] = value
delete object.name | delete object[name]
Property
Named collection of attributes
ES5 added functionality to define properties and added Get, Set functions
Attributes: value, writable, configurable, enumerable, get, set

5. Demo – Objects

6. Object Types
Arrays
Special object with index as property names (not associative)
Has properties like: length, sort(), filter()
RegEx
Regular expression object
2 primary methods exec() returns a match and test() returns boolean
Functions
An object which can be invoked with parentheses ()

7. Demo – Objects
Revisited

8. Other Types
null
Nothing
undefined
Less than nothing

9. Functions
Composition
Made up of 4 parts: function, name (optional), parameters, set of statements
2 additional parameters: arguments object & this (invocation context)
Invocation
Method – this is the local object
Function – this is the global object
Apply – this is passed as a parameter
Constructor – this is the new object
Calling
Assigning less parameters will make them undefined

10. Demo – Invoking Functions

11. Inheritance with Prototypes
Prototype with functions
All functions have a property prototype as a base object
Use new keyword with function invocation to create new objects
Constructor functions should start with a capital letter
Inheritance
If object doesn’t have a property look in base object

12. Demo - Prototyping

13. Questions?