JavaScript

Regular Expression with Multiple Matches and Named Capture Groups

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Demonstrates regular expressions with named capture groups and multiple matches. JavaScript

var success = false;

var sb = new CkStringBuilder();
var crlf = true;
sb.AppendLine("Name: John Smith",crlf);
sb.AppendLine("Name: Jack Johnson",crlf);
sb.AppendLine("Name: Mary Adams",crlf);

console.log(sb.GetAsString());

// We have the following string:
// Name: John Smith
// Name: Jack Johnson
// Name: Mary Adams

var pattern = "Name:\\s+(?<first>\\w+)\\s+(?<last>\\w+)";
var json = new CkJsonObject();
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());

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

// {
//   "named": {
//     "first": 1,
//     "last": 2
//   },
//   "match": [
//     {
//       "group": [
//         {
//           "cap": "Name: John Smith",
//           "idx": 0,
//           "len": 16
//         },
//         {
//           "cap": "John",
//           "idx": 6,
//           "len": 4
//         },
//         {
//           "cap": "Smith",
//           "idx": 11,
//           "len": 5
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Name: Jack Johnson",
//           "idx": 18,
//           "len": 18
//         },
//         {
//           "cap": "Jack",
//           "idx": 24,
//           "len": 4
//         },
//         {
//           "cap": "Johnson",
//           "idx": 29,
//           "len": 7
//         }
//       ]
//     },
//     {
//       "group": [
//         {
//           "cap": "Name: Mary Adams",
//           "idx": 38,
//           "len": 16
//         },
//         {
//           "cap": "Mary",
//           "idx": 44,
//           "len": 4
//         },
//         {
//           "cap": "Adams",
//           "idx": 49,
//           "len": 5
//         }
//       ]
//     }
//   ]
// }

// The capture group index is obtained by looking up the name in the JSON result.
// For example:

var idx_first = json.IntOf("named.first");
var idx_last = json.IntOf("named.last");

var i = 0;
var matchCount = json.SizeOfArray("match");
while (i < matchCount) {
    console.log("Match " + (i+1) + ":");
    json.I = i;

    json.J = idx_first;
    console.log("first: " + json.StringOf("match[i].group[j].cap"));

    json.J = idx_last;
    console.log("first: " + json.StringOf("match[i].group[j].cap"));

    console.log("");
    i = i+1;
}

// Output is: 

// Match 1:
// first: John
// first: Smith
// 
// Match 2:
// first: Jack
// first: Johnson
// 
// Match 3:
// first: Mary
// first: Adams