Implements named parameters on javascript regexp with use of getters.

regexp-named-parameters.js

/**
 * The idea here is to support named regexp parameters by returning a proxy with a getter function
 * TODO add Proxy
 */
class RegExp2 extends RegExp {
    constructor(regexpStr, ...names) {
        super(regexpStr)
        this.names = names;
    }
    exec(str) {
        return new RegExp2Result(this, super.exec(str));
    }
}

class RegExp2Result {
    constructor(regexp2, matches) {
        this.regexp2 = regexp2;
        this.matches = matches;
        /*return new Proxy(this, {
            get: (target, name) => {
                if (matches === null) {
                    return null;
                }
                let index = target.names.indexOf(name);
                if (index === -1) {
                    return false;
                }
                // The first element in the matches array is the full string
                return this.matches[index + 1];
            }
        });*/
        for (var i in regexp2.names) {
            var name = regexp2.names[i];
            Object.defineProperty(this, name, { get: function () {
                if (matches === null) {
                    return null;
                }
                let index = regexp2.names.indexOf(name);
                if (index === -1) {
                    return false;
                }
                // The first element in the matches array is the full string
                return matches[index + 1];
            } });
        }
    }
}

var chai = require('chai')
  , expect = chai.expect
  , should = chai.should();

var re2 = new RegExp2('hello (\\w+)', ['name']);
var re2resmatch = re2.exec('hello john');
re2resmatch.name.should.equal('john');
expect(re2resmatch.name2).to.be.undefined;
var re2resnomatch = re2.exec('hello');
expect(re2resnomatch.name).to.be.null;