How to Ignore Optional Whitespace in Regular Expressions?

Optional Whitespace in Regular Expressions

When parsing HTML or other text formats, it's often necessary to ignore optional whitespace characters. To achieve this, you can modify your regular expression pattern using the following conventions:

• s?: Add this expression immediately after an attribute name to indicate that an optional whitespace character is allowed.
• ?: This quantifier indicates that the preceding character may occur once or not at all.
• s*: If multiple optional whitespace characters are allowed, use this expression.
• *: This quantifier indicates that the preceding character may occur zero or more times.

For example, if you want to allow optional spaces between attribute names and values, modify your pattern to the following:

#<a href\s?="(.*?)" title\s?="(.*?)"><img alt\s?="(.*?)" src\s?="(.*?)"[\s*]width\s?="150"[\s*]height\s?="(.*?)"></a>#

This pattern will match HTML elements like these:

<code class="html"><a href="/wiki/File:Sky1.png" title="File:Sky1.png"><img alt="Sky1.png" src="http://media-mcw.cursecdn.com/thumb/5/56/Sky1.png/150px-Sky1.png" width="150" height="84"></a></code>

<code class="html"><a href="/wiki/File:TallGrass.gif" title="File:TallGrass.gif"><img alt="TallGrass.gif" src="http://media-mcw.cursecdn.com/3/34/TallGrass.gif" width="150"height="150"></a></code>

Note that the extra [space] characters in the original pattern are not included in this modified version.

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