Datatypes and variables

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Revision as of 21:07, 15 July 2009 by Michael (talk | contribs)
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Introduction to JavaScript
  • Integrate JavaScript on webpages
    • Internal JavaScript
    • External JavaScript
    • Inline JavaScript
  • Datatypes and variables
    • Datatypes overview
    • Variables declaration
  • Arrays
    • Implementation
    • Declaration
    • array as object -> properties and methods
    • Anonymous arrays
    • associative arrays/hashtables
  • Functions
    • Declaration
    • Parameters
    • Default values for parameters and variable length parameter lists
    • return values
    • callback functions
    • anonymous functions
  • Objects
    • Class definition, object initialisation, singletons
    • Prototyping concept and inheritance
    • Anonymous objects
    • Objects as associative arrays

Data types

Though JavaScript is a weakly typed programming language, there are some data types between which JavaScript sometimes variables automatically converts:


Null means variable has no value at all. Do not confuse null with 0 (zero)! 0 is just a number, null means just no value or a empty or non-existent reference.


A value that is undefined is a value held by a variable right after it has been created and before a value has been assigned to it.