Node.js

Regular Expression with Capture Groups

See more Regular Expressions Examples

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

Demonstrates the following PCRE2 regular expression:

See the sample code below.

Name:\s+(\w+)\s+(\w+),\s+Email:\s+(\S+)

And apply it to this string:

Name: John Smith, Email: john.smith@example.com

---

Regex Components Explained

Part	Meaning	Matched Text
"Name:"	Matches the literal text "Name:"	"Name:"
"\s+"	Matches one or more whitespace characters (spaces, tabs, etc.)	(space)
"(\w+)"	Capture Group 1: One or more word characters ("a-zA-Z0-9_")	"John"
"\s+"	More whitespace	(space)
"(\w+)"	Capture Group 2: Another word (the last name)	"Smith"
","	A literal comma	","
"\s+"	Whitespace again	(space)
"Email:"	Matches the literal "Email:"	"Email:"
"\s+"	Whitespace	(space)
"(\S+)"	Capture Group 3: One or more non-whitespace characters	"john.smith@example.com"

---

Matches for Your Example String

String:

"Name: John Smith, Email: john.smith@example.com"

Regex Match Groups:

Group	Captured Value
Group 1	"John"
Group 2	"Smith"
Group 3	"john.smith@example.com"

---

Notes on Character Classes

• \w matches [a-zA-Z0-9_] — so it doesn’t include punctuation like a period.
• \S matches any non-whitespace character, so it’s good for capturing an email.

Node.js

NODEJS_PRELUDE

function chilkatExample() {

    var success = false;

    var subject = "Name: John Smith, Email: john.smith@example.com";
    var pattern = "Name:\\s+(\\w+)\\s+(\\w+),\\s+Email:\\s+(\\S+)";

    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());

    //  This is the JSON with the match information.
    //  See the JSON parsing code below to get the matched capture group values.

    //  Important:  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

    //  {
    //    "match": [
    //      {
    //        "group": [
    //          {
    //            "cap": "Name: John Smith, Email: john.smith@example.com",
    //            "idx": 0,
    //            "len": 47
    //          },
    //          {
    //            "cap": "John",
    //            "idx": 6,
    //            "len": 4
    //          },
    //          {
    //            "cap": "Smith",
    //            "idx": 11,
    //            "len": 5
    //          },
    //          {
    //            "cap": "john.smith@example.com",
    //            "idx": 25,
    //            "len": 22
    //          }
    //        ]
    //      }
    //    ]
    //  }

    var cap;
    var i = 0;
    var matchCount = json.SizeOfArray("match");
    while (i < matchCount) {
        console.log("Match " + (i+1) + ":");
        json.I = i;
        var j = 0;
        var numCaptureGroups = json.SizeOfArray("match[i].group");
        while (j < numCaptureGroups) {
            json.J = j;
            cap = json.StringOf("match[i].group[j].cap");
            console.log(j + ": " + cap);
            j = j+1;
        }

        i = i+1;
    }

    //  Capture group 0 always contains the entire match — that is, the portion of the input string that matches the full regular expression.

    //  Output

    //  Match 1:
    //  0: Name: John Smith, Email: john.smith@example.com
    //  1: John
    //  2: Smith
    //  3: john.smith@example.com

}

chilkatExample();