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reRedOrBlack

In this,

reRedOrBlack

matches either

“red”

“black”

, and testing against each string yields

“true”

Because the alternation is contained in a group, whichever alternative is matched is stored in

RegExp.$1

for later use (as well as being available as

in the expression). In the first test,

RegExp.$1

is equal to

“red”

; in the second, it is equal to

“blue”

You can specify as many options as you’d like just by adding more alternatives and more alternation

operators:

var sToMatch1 = “red”;

var sToMatch2 = “black”;

var sToMatch3 = “green”;

var reRedOrBlack = /(red|black|green)/;

alert(reRedOrBlack.test(sToMatch1)); //outputs “true”

alert(reRedOrBlack.test(sToMatch2)); //outputs “true”

alert(reRedOrBlack.test(sToMatch3)); //outputs “true”

A more practical use of an OR pattern is to remove inappropriate words from user input, which can be

very important in online forums. By using an OR pattern with the inappropriate words and the

replace()

method, you can easily strip out any offensive material before it is posted:

var reBadWords = /badword|anotherbadword/gi;

var sUserInput = “This is a string using badword1 and badword2.”;

var sFinalText = sUserInput.replace(reBadWords, “****”);

alert(sFinalText); //output “This is a string using **** and ****”

This example specifies

“badword1”

and

“badword2”

to be inappropriate. The expression

reBadWords

uses the OR operator to specify both words (note that both the global and case-insensitive flags are set).

When the

replace()

method is used, each of the inappropriate words is replaced with four asterisks

(the proverbial four-letter word representation).

You can also replace inappropriate words using an asterisk to replace each letter, meaning that the

replacement text contains the same number of characters as the word in question. This can be done

using a function as the second argument to the

replace()

method:

var reBadWords = /badword|anotherbadword/gi;

var sUserInput = “This is a string using badword1 and badword2.”;

var sFinalText = sUserInput.replace(reBadWords, function(sMatch) {

return sMatch.replace(/./g, “*”);

});

alert(sFinalText); //output “This is a string using ******* and **************”

In this code, the function passed in as the second argument to

replace()

actually uses another regular

expression. When the function is executed,

sMatch

contains one of the inappropriate words. The fastest

way to replace each character with an asterisk is to use the

replace()

method on

sMatch

, specifying a

pattern that matches any character (the period) and replacing it with an asterisk (note that the global flag

has been set as well). Techniques such as this can ensure that inappropriate remarks cannot get posted to

your online forum or bulletin board.

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