questions.jsâThe JavaScript Source File
Letâs continue with questions.js
, the
JavaScript source file called by administer.html
,
shown in Example 2.2.
Example 2-2. The Beginning of the questions.js Source Code
1 function question(answer, support, question, a, b, c, d) { 2 this.answer = answer; 3 this.support = support; 4 this.question = question; 5 this.a = a; 6 this.b = b; 7 this.c = c; 8 this.d = d; 9 return this; 10 } 11 var units = new Array( 12 new question("a", "The others are external objects.", 13 "Choose the built-in JavaScript object:", "Image", "mimeType", 14 "Password", "Area"), 15 // and so on ... 16 }
This is, of course, an abbreviated version of the file. Array
units is much longer (75 elements in all),
but this shows you that each element of
units is a question object as defined in
function question()
in lines 1-10.
This application is based on user-defined objects (objects that you and I declare). If the concept of JavaScript objects seems obscure, check Netscapeâs documentation at http://developer.netscape.com/docs/manuals/communicator/jsguide4/model.htm. It will help you better understand the JavaScript Object Model. In the meantime, use the next few paragraphs as a crash course.
An object is a set of structured data. Each object can own or have
associated with it two types of entitiesâproperties and
methods. Properties have something, such as the
number 6, the expression a * b
, or the string âJimmy.â
Methods do something, such as calculate ...
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