compile Method (Windows Scripting - JScript)

Compiles a regular expression into an internal format for faster execution.


rgExp.compile(pattern, [flags]) 


  • rgExp
    Required. An instance of a Regular Expression object. Can be a variable name or a literal.

  • pattern
    Required. A string expression containing a regular expression pattern to be compiled

  • flags
    Optional. Available flags, which may be combined, are:

    • g (global search for all occurrences of pattern)

    • i (ignore case)

    • m (multiline search)


The compile method converts pattern into an internal format for faster execution. This allows for more efficient use of regular expressions in loops, for example. A compiled regular expression speeds things up when reusing the same expression repeatedly. No advantage is gained, however, if the regular expression changes.

The following example illustrates the use of the compile method:

function CompileDemo(){
   var rs;
   var s = "AaBbCcDdEeFfGgHhIiJjKkLlMmNnOoPp"
   // Create regular expression for uppercase only.
   var r = new RegExp("[A-Z]", "g");
   var a1 = s.match(r)              // Find matches.
   // Compile the regular expression for lowercase only.
   r.compile("[a-z]", "g");
// Find matches.
   var a2 = s.match(r)              
   return(a1 + "\n" + a2);


Version 3

Applies To: Regular Expression Object (Windows Scripting - JScript)

Change History




March 2009

Fixed syntax bug in sample code.

Content bug fix.

See Also

Regular Expression Syntax (Scripting)