Just came up with this simple method for removing extra whitespace from a string using regular expressions and the String.replace() method. Many examples found on the web involve looping through the entire string and evaluating individual characters which can be an expensive operation. Using regular expressions, as shown below, can definitely save some keystrokes and processing.

// -- String with tab, multiple spaces and newline char
var testString:String = 'here is a tabthere are six spaces      here is a new linennext line';

// -- Test expression
var whitespace:RegExp = /(\t|\n|\s{2,})/g;

trace( 'testString pre-replace: ' + testString );

// -- Re-assign the value of testString to the result of replace() mehtod
testString = testString.replace( whitespace, ' ' );

trace( 'testString post-replace: ' + testString )

The replace() method turns all multiple spaces, tabs and newline characters into single spaces.