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By using parentheses creatively in a regular expression a sub-pattern can be marked out such that when a match occurs, that sub-pattern can be extracted.
Here is a pattern that matches a date format:
/[0-9]{2}-[a-zA-Z]{3}-[0-9]{4}/
We might want to extract just the month name. We can place parentheses around that so it can be extracted later. Like this:
/[0-9]{2}-([a-zA-Z]{3})-[0-9]{4}/
The example shows how this works:
<HTML>
<HEAD>
</HEAD>
<BODY>
<SCRIPT>
// Make the RegExp from a literal
myRegExp = /[0-9]{2}-([a-zA-Z]{3})-[0-9]{4}/;
// Create the input search string
myString = "01-Jan-1954";
// Run the search
myArray = myRegExp.exec(myString);
// How many items are there in the array
document.write(myArray.length);
document.write("<BR>");
// Display the source string
document.write(myArray[0]);
document.write("<BR>");
// Display the month name sub-match
document.write(myArray[1]);
document.write("<BR>");
</SCRIPT>
</BODY>
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| RegExp pattern - repetition | Up | Regular expression |
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. | ||