Perform grep search

Question

Hi folks,
I was wondering whether it was possible to find and replace using grep. I have the find and replace thing sorted, but I need it to be flexible enough to select any number and alter the value by a set amount. I have done this in InDesign but have become stuck with Illustrator.
I have tried to use an adapted version of the search script from this thread: (CarlosCanto)
var multiplier = parseFloat(2.5);
var search_string = /[-]*[0-9][0-9,.]*\\b/gi;
var replace_string = search_string * multiplier;
var text_frames = active_doc.textFrames;
if (text_frames.length > 0) {
    for (var i = 0 ; i < text_frames.length; i++) {
        var this_text_frame = text_frames[i];
        var new_string = this_text_frame.contents.replace(search_string, replace_string);
        if (new_string != this_text_frame.contents) {
            this_text_frame.contents = new_string;
This simply returns 'undefined'
Do I need to invoke a grep function to parse the pattern through?
Any help would be wonderful.
Thanks

Answer 1

This is what I meant by using UnitValues…
#target illustrator
var idoc = app.activeDocument;
var ilayer = idoc.layers['measurements'];
var oldUnit = prompt ( 'Enter old unit string:', 'inch', 'Convert Units' );
var newUnit = prompt ( 'Enter new unit string:', 'mm', 'Convert Units' );
for ( var i = 0; i < ilayer.textFrames.length; i++ ) {
     var itext = ilayer.textFrames[i].contents;
     var mValue = new UnitValue( Number( itext ),oldUnit );
     ilayer.textFrames[i].contents = mValue.as( newUnit );
If you were to look up the strings table you will see yards, miles, meters, kilometers etc… Plus all the usual stuff just a little less math for you to input… Personally I would still use a dialog with 2 drop down lists for old & new units… That should be simple enough to do…