Regular Expressions

Encoding special characters in a block of HTML or other code can be a pain because there might already be ampersands there that impart encoding. This might be an ampersand that has already been encoded with a &, or it might be an ampersand in the code as an if statement or similar.

Use the following regular expression to find any ampersand that hasn't already been encoded.

([^&])&(?!#?[a-zA-Z0-9]{2,6};|\$|&)

When using replace, you can turn any ampersand into & by using the following replace.

$1&

The only problem with this statement is when the code uses a & operator as part of a statement to do bitwise operations.

The reverse of turning ASCII text into HTML is to convert HTML into ASCII. And to this end here is a little function that does this.

Here are some of the regular expressions that I frequently use.

Find a blank line

^$

Spaces

[ \t]+

You can use this to break a text string apart into words.

Date

\d{1,2}(\-|\/|\.)\d{1,2}\1\d{4}

This will match anything in the format mm/dd/yyyy, or even dd/mm/yyyy.

[A-Z][a-z][a-z] [0-9][0-9]*, [0-9]{4}

Will match a formatted date, such as Mar 24, 2007.

Time

([1-9]|1[0-2]):[0-5]\d(:[0-5]\d(\.\d{1,3})?)?

This will match HH:MM or HH:MM:SS or HH:MM:SS.mmm.

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