
Contents > Developing ColdFusion MX Applications > Using Regular Expressions in Functions > Using backreferences > Using backreferences in replacement strings

Using backreferences in replacement strings

You can use backreferences in the replacement string of both the REReplace and REReplaceNoCase functions. For example, to replace the first repeated word in a text string with a single word, use the following syntax:

REReplace("There is is a cat in in the kitchen",
"([A-Za-z ]+)\1","\1")

This results in the sentence:

"There is a cat in in the kitchen"

You can use the optional fourth parameter to REReplace, scope, to replace all repeated words, as in the following code:

REReplace("There is is a cat in in the kitchen",
"([A-Za-z ]+)\1","\1","ALL")

This results in the following string:

"There is a cat in the kitchen"

The next example uses two backreferences to reverse the order of the words "apples" and "pears" in a sentence:

<cfset astring = "apples and pears, apples and pears, apples and pears">
<cfset newString = REReplace("#astring#", "(apples) and (pears)",
"\2 and \1","ALL")>

In this example, you reference the subexpression (apples) as \1 and the subexpression (pears) as \2. The REReplace function returns the string:

"pears and apples, pears and apples, pears and apples"

Note: To use backreferences in either the search string or the replace string, you must use parentheses within the regular expression to create the corresponding subexpression. Otherwise, ColdFusion throws an exception.


Contents > Developing ColdFusion MX Applications > Using Regular Expressions in Functions > Using backreferences > Using backreferences in replacement strings

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