(Node.js) Regular Expression Replace Capture Groups

See more Regular Expressions Examples

Note: Chilkat uses PCRE2. See PCRE2 Regular Expressions
Also see: PCRE2 Performance

Note: This example requires Chilkat v11.1.0 or greater.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-mac-universal');
}

function chilkatExample() {

    var success = false;

    var subject = "John Anders, +_+_+ Mary Robins $$$$";
    var pattern = "(?<first>\\w+)\\s+(?<last>\\w+)";

    var sb = new chilkat.StringBuilder();
    sb.Append(subject);

    var json = new chilkat.JsonObject();
    json.EmitCompact = false;

    var timeoutMs = 2000;
    var numMatches = sb.RegexMatch(pattern,json,timeoutMs);
    if (numMatches < 0) {
        // Probably an error in the regular expression.
        // Suggestion: Use AI to help create and/or diagnose regular expressions.
        console.log(sb.LastErrorText);
        return;
    }

    // Examine the matches:
    console.log(json.Emit());

    // There are 2 matches:

    // {
    //   "named": {
    //     "first": 1,
    //     "last": 2
    //   },
    //   "match": [
    //     {
    //       "group": [
    //         {
    //           "cap": "John Anders",
    //           "idx": 0,
    //           "len": 11
    //         },
    //         {
    //           "cap": "John",
    //           "idx": 0,
    //           "len": 4
    //         },
    //         {
    //           "cap": "Anders",
    //           "idx": 5,
    //           "len": 6
    //         }
    //       ]
    //     },
    //     {
    //       "group": [
    //         {
    //           "cap": "Mary Robins",
    //           "idx": 19,
    //           "len": 11
    //         },
    //         {
    //           "cap": "Mary",
    //           "idx": 19,
    //           "len": 4
    //         },
    //         {
    //           "cap": "Robins",
    //           "idx": 24,
    //           "len": 6
    //         }
    //       ]
    //     }
    //   ]
    // }

    // To replace capture groups, write code to examine each capture group within
    // each match, and provide a replacement string.
    // Then call RegexReplace.

    // For example, let's capitalize the first names, and add append "on" to the last name.
    // After doing replacements, we should get:  JOHN Anderson, +_+_+ MARY Robinson $$$$

    var firstNameIdx = json.IntOf("named.first");
    var lastNameIdx = json.IntOf("named.last");

    var sbTemp = new chilkat.StringBuilder();

    var i = 0;
    numMatches = json.SizeOfArray("match");
    while (i < numMatches) {

        json.I = i;

        // The replacement string for the first name will be all uppercase.
        json.J = firstNameIdx;
        sbTemp.Clear();
        json.StringOfSb("match[i].group[j].cap",sbTemp);
        sbTemp.ToUppercase();
        json.UpdateSb("match[i].group[j].rep",sbTemp);

        // Append "on" to the last name.
        json.J = lastNameIdx;
        sbTemp.Clear();
        json.StringOfSb("match[i].group[j].cap",sbTemp);
        sbTemp.Append("on");
        json.UpdateSb("match[i].group[j].rep",sbTemp);

        i = i+1;
    }

    // The JSON now has replacement strings:
    console.log(json.Emit());

    // {
    //   "named": {
    //     "first": 1,
    //     "last": 2
    //   },
    //   "match": [
    //     {
    //       "group": [
    //         {
    //           "cap": "John Anders",
    //           "idx": 0,
    //           "len": 11
    //         },
    //         {
    //           "cap": "John",
    //           "idx": 0,
    //           "len": 4,
    //           "rep": "JOHN"
    //         },
    //         {
    //           "cap": "Anders",
    //           "idx": 5,
    //           "len": 6,
    //           "rep": "Anderson"
    //         }
    //       ]
    //     },
    //     {
    //       "group": [
    //         {
    //           "cap": "Mary Robins",
    //           "idx": 19,
    //           "len": 11
    //         },
    //         {
    //           "cap": "Mary",
    //           "idx": 19,
    //           "len": 4,
    //           "rep": "MARY"
    //         },
    //         {
    //           "cap": "Robins",
    //           "idx": 24,
    //           "len": 6,
    //           "rep": "Robinson"
    //         }
    //       ]
    //     }
    //   ]
    // }

    // Call RegexReplace to update the StringBuilder with the replacements.
    success = sb.RegexReplace(json);
    if (success == false) {
        console.log(sb.LastErrorText);
        return;
    }

    console.log("Result after doing replacements:");
    console.log(sb.GetAsString());

    // Result after doing replacements:
    // JOHN Anderson, +_+_+ MARY Robinson $$$$

}

chilkatExample();