December 2008
Beginner
396 pages
10h 18m
English
Content preview from Learning JavaScript, 2nd EditionBecome an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
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Chapter 13. Creating Custom JavaScript Objects
Previous chapters made use of existing objects, defined as part of the JavaScript language or inherited as part of the browser Document Object Model (DOM). This chapter focuses on how you can create your own custom JavaScript objects and package them for reuse across many applications.
The JavaScript Object and Prototyping
An object in JavaScript is a complex construct usually consisting of
a constructor as well as zero or more methods and/or properties.
Additionally, all objects in JavaScript derive functionality from the
standard JavaScript Object.
The Object itself is not
particularly interesting. What Object
does is provide the framework for creating new objects. Unlike in other
programming languages, though, the JavaScript Object doesn’t provide framework functionality
to new objects via traditional object-oriented inheritance and the concept
of classes. Instead, JavaScript derives its object functionality from a
concept called prototyping.
Prototyping
In a language such as Java or C++, to create a class as an extension of another, you define the class in such a way that it inherits the functionality of the higher-level object and overrides whatever functionality you don’t want.
JavaScript, on the other hand, provides for a
constructor, via Object, that
allows you to create new objects. It is the Object constructor that allocates the memory
for the object, including all of its properties. The Object also provides a prototype property ...
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