This section provides a quick description of indexed properties and indexed methods. A tutorial example is provided on how to create and access indexed properties and indexed methods.
JavaScript also supports objects with indexed properties with the following features:
An indexed property is a property with an index number instead of a property name.
An indexed property can not be accessed with the dot (.) operator.
An indexed property can be accessed with the associate array operator (['index']).
An indexed property can also be accessed with the array operator ([index]).
An indexed property can be assigned with a function to become an indexed method.
Here is a tutorial example on how to define and access object's indexed properties and indexed methods
in two formats: array format and associate array format:
<html>
<!-- Object_Indexed_Properties.html
Copyright (c) 2008 by Dr. Herong Yang, http://www.herongyang.com/
-->
<head>
<title>Objects with Indexed Properties</title>
</head>
<body>
<pre>
<script type="text/javascript">
// Using "this" to get the properties
function myToString() {
return '"'+this.title + '" by '+this.author;
}
// Using object literal format
var myBook = {
author: "Herong Yang",
title: "JavaScript Tutorials",
3: 2008,
price: "Free",
4: myToString
};
// Adding a new indexed property
myBook[9] = "Programming";
// An index property can not be accessed with (.)
// document.writeln("myBook.3: "+myBook.3);
// Getting indexed property values
document.writeln("myBook[3]: "+myBook[3]);
document.writeln("myBook['3']: "+myBook['3']);
document.writeln("myBook[4]: "+myBook[4]);
document.writeln("myBook[9]: "+myBook[9]);
// Checking property data types
document.writeln();
document.writeln(myBook[4]());
</script>
</pre>
</body>
</html>
The output of this tutorial example matches my expectation:
myBook[3]: 2008
myBook['3']: 2008
myBook[4]: function myToString() {
return "\"" + this.title + "\" by " + this.author;
}
myBook[9]: Programming
"JavaScript Tutorials" by Herong Yang
