JavaScript: String.prototype.match & RegExp.prototype.exec

JavaScript-RegExp.js

// A scratchpad testing the differences between:
// - `String.prototype.match` (with & without `g` flag)
// - `RegExp.prototype.exec`  (with & without `g` flag)

const str = "A string\nWith 2 endlines\n";

(function () {
  console.info("==== String.prototype.match GLOBAL ====");
  const re = /(\w)(?<NamedGroup1>\w)\n/g;
  // Returns an array containing **all** string segments matching the **whole regex**
  // Extra properties **NOT included**
  // RegExp is non-stateful
  // Capturing groups are **NOT included**

  console.log(str.match(re)); // ["ng\n", "es\n"]
  console.log(str.match(re)); // ["ng\n", "es\n"]
  console.log(str.match(re)); // ["ng\n", "es\n"]
})();

(function () {
  console.info("==== String.prototype.match ONCE ====");
  const re = /(\w)(?<NamedGroup1>\w)\n/;
  // Returns an array containing the **first** match of the whole regex, followed by **other capturing groups**
  // Extra properties included at the array object: "index", "input", "groups"
  // RegExp is non-stateful
  // Capturing groups are included

  console.log(str.match(re)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}})
  console.log(str.match(re)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}})
  console.log(str.match(re)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}})
})();

(function () {
  console.info("==== RegExp.prototype.exec GLOBAL ====");
  const re = /(\w)(?<NamedGroup1>\w)\n/g;
  // Returns an array containing the **successive** match of the whole regex, followed by **other capturing groups**
  // Extra properties included at the array object: "index", "input", "groups"
  // RegExp is **Stateful**
  // Capturing groups are included

  console.log(re.exec(str)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}});
  console.log(re.exec(str)); // Object.assign(["es\n", "e", "s"], {index: 22, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "s"}});
  console.log(re.exec(str)); // null
})();

(function () {
  console.info("==== RegExp.prototype.exec ONCE ====");
  const re = /(\w)(?<NamedGroup1>\w)\n/;
  // Returns an array containing the **first** match of the whole regex, followed by **other capturing groups**
  // Extra properties included at the array object: "index", "input", "groups"
  // RegExp is non-stateful(?)
  // Capturing groups are included

  console.log(re.exec(str)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}});
  console.log(re.exec(str)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}});
  console.log(re.exec(str)); // Object.assign(["ng\n", "n", "g"], {index: 6, input: "A string\nWith 2 endlines\n", groups: {NamedGroup1: "g"}});
})();