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The prototype for an array is the original Array prototype object.
Array objects inherit many methods and properties from their prototype parent. Enquiring the prototype of a an object whose provenance is unknown will tell you what sort of object that is.
Array objects inherit these properties from the built-in Array prototype:
Array.constructor
Array.prototype
Array objects inherit these methods from the built in Array prototype:
Array.join()
Array.reverse()
Array.sort()
Array.toString()
Array instances provide these properties themselves even if the prototype has them:
Array.length
The example demonstrates how to provide extensions to all instances of this class by adding a function to the prototype object.
<HTML>
<HEAD>
</HEAD>
<BODY>
<SCRIPT>
// Define a function that duplicates the item at the end of
// the array
function dupe()
{
if(this.length != 0)
{
myTail = this[this.length-1];
this[this.length] = myTail;
return myTail;
}
}
// Register the new function
Array.prototype.dupe = dupe;
// Create an array and test the Array.dupe() method
myArray = new Array("AAA", "BBB", "CCC");
document.write("Array<BR>")
displayArrayAsTable(myArray);
document.write("Array.dupe()<BR>")
document.write(myArray.dupe())
document.write("<BR>")
document.write("<BR>")
document.write("Array after dupe() call<BR>")
displayArrayAsTable(myArray);
// Display an array in a table
function displayArrayAsTable(anArray)
{
myLength = anArray.length;
document.write("<TABLE BORDER=1>");
for(myIndex = 0; myIndex < myLength; myIndex++)
{
document.write("<TR><TD>");
document.write(myIndex);
document.write("</TD><TD>");
document.write(anArray[myIndex]);
document.write("</TD></TR>");
document.write("</TD></TR>");
}
document.write("</TABLE><BR><BR>")
}
</SCRIPT>
</BODY>
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| Array.pop() | Up | Array.push() |
JavaScript Programmer's Reference, Cliff Wootton Wrox Press (www.wrox.com) Join the Wrox JavaScript forum at p2p.wrox.com Please report problems to support@wrox.com © 2001 Wrox Press. All Rights Reserved. Terms and conditions. | ||