Regular Expressions in Javascript

Now that we can successfully build a Regular Expression, how do we implement it into our Javascript code ? Well, if we are doing a simple replace we could do something like :

<script language="javascript">
 
// our string that we are going to operate on
var inputstr="this is my long test string with the word long in it, hope that the Regular Expression does not take too LONG.";
 
// an empty string to hold the result
var outputstr="";
 
// our Regular Expression
var regex=/long/gi;
 
// run the Regular Expression to replace any match to our Regular Expression with the word short.
outputstr=inputstr.replace(regex,"short");
 
// popup the string which should be
//"this is my short test string with the word short in it, hope that the Regular Expression does not take too short."
alert(outputstr);
 
</script>

A Match is performed in a similar way, although this time we want to let the user know if there is match or not :

<script language="javascript">
 
// our string that we are going to operate on
var inputstr="A1234";
 
// our Regular Expression
var regex=/^[A-Z]\d{4}$/g;
 
// do the comparison, if we have a match
if (regex.test(inputstr))
{
      alert("Matches");
}
else
{
      alert("Does not match");
}
 
</script>

Although in both of these case the input and output variables could be fields on a form and the result of the test is likely to be a little more complex that a simple popup, but I leave that for you to work into your code as the need arises.

This concludes this introduction to Regular Expressions, the conclusion contains links to futher reading on the subject both on the internet as well as some books.