ExtendScript to find string matching regex and replace with substring using backref ($n)

@frameexpert , Thanks to you I can finally claim victory! Your videos told me what I needed to know about how to work with capture groups. My script now does all three of the things I needed to accomplish. This is what I ended up with:

#target framemaker
#include "ApplyCharFmt.jsx"

main ();

function main () {
    var doc;
    
    doc = app.ActiveDoc;
    if (doc.ObjectValid () === 1) {
        processDoc (doc);        
    }
    return 0;
}

function processDoc (doc) {
    var regex, pgf, text, matches;

//    regex for zero or more chars inside straight or curly double quotes
//    \u201c = “    \u201d = ”     i = ignore case      g = greedy match mode
    regex = /["\u201c](.*?)["\u201d]/ig; 

    if (app.Displaying === 1) {
        app.Displaying = 0;
    }

    pgf = doc.MainFlowInDoc.FirstTextFrameInFlow.FirstPgf;
    while (pgf.ObjectValid () === 1) {
        text = getPgfText (pgf);
        if (regex.test (text) === true) {
            matches = getPgfRegexMatches (regex, text);
            processPgf (pgf, matches, doc);
        }
        pgf = pgf.NextPgfInFlow;    
    }

    if (app.Displaying === 0) {
        app.Displaying = 1;
        doc.Redisplay();
    }
}

function getPgfText(pgf) {
    var text, textList, count, i;
    text = "";
    textList = pgf.GetText (Constants.FTI_String);
    count = textList.length;
    for (i = 0; i < count; i += 1) {
        text += (textList[i].sdata);    
    }
    return text;
}

function getPgfRegexMatches (regex, text) {
    var matches, match, matchObj;
    matches = [];
    while (match = regex.exec (text)) {
        matchObj = {};
        matchObj.value = match[0];
        matchObj.beginOffset = match.index;
        matchObj.endOffset = regex.lastIndex;
        matchObj.submatches = getSubmatches (match);
        matches.push (matchObj);
    }
    regex.lastIndex = 0;
    
    function getSubmatches (match) {    
        var submatches, count,  i;
        submatches = [];
        count = match.length;
        for (i = 1; i < count; i += 1) {
            submatches.push (match[i]);
        }        
        return submatches;
    }
    return matches;
}

function processPgf (pgf, matches, doc) {
    
    var count, i, matchObj, textLoc, findParams, textRange, foundPgf, newTxt, newTxtEnd, newTxtRange;
    
    count = matches.length - 1;
    for (i = count; i >= 0; i -= 1) {
        matchObj = matches[i]; 
        textLoc = new TextLoc (pgf, matchObj.beginOffset);
        doc.TextSelection = new TextRange (textLoc, textLoc);
        findParams = getFindParams(matchObj.value); 
        textRange = doc.Find (textLoc, findParams);
        foundPgf = textRange.beg.obj;
        if ((foundPgf.ObjectValid () === 1) && (foundPgf.id === pgf.id)) {
            newTxt = matchObj.submatches.join ("");
            doFindChange (textRange, newTxt, doc); 
            newTxtEnd = new TextLoc (foundPgf, (matchObj.endOffset - 2));
            newTxtRange = new TextRange (textLoc, newTxtEnd);
            ApplyCharFmt (doc, newTxtRange, "Bold");      
        }
        else {
            return;
        }
    }
}

function getFindParams (text) {
    // Set up the find parameters
    var findParams = AllocatePropVals (4);    

    findParams[0].propIdent.num = Constants.FS_FindText;    
    findParams[0].propVal.valType = Constants.FT_String;    
    findParams[0].propVal.sval = text;    
   
    findParams[1].propIdent.num = Constants.FS_FindWrap;    
    findParams[1].propVal.valType = Constants.FT_Integer;    
    findParams[1].propVal.ival = false;  
     
    findParams[2].propIdent.num = Constants.FS_FindCustomizationFlags;
    findParams[2].propVal.valType = Constants.FT_Integer;
    findParams[2].propVal.ival = Constants.FF_FIND_USE_REGEX;

    findParams[3].propIdent.num = Constants.FS_RegexFlavour;
    findParams[3].propVal.valType = Constants.FT_Integer;
    findParams[3].propVal.ival = Constants.FR_USE_PERL;
    
    return findParams;
}

function doFindChange (textRange, change, doc) {
    doc.DeleteText (textRange);
    if (change) {
        doc.AddText (textRange.beg, change);
    }
}