RegExpのクローンを試す

cloneRegExp.js

function cloneRegExp (reg) {
    if (! (reg instanceof RegExp)) throw new Error('TypeError: "reg" is not "RegExp"');

    var _source = reg.source;
    var _string = reg.toString();
    var pos     = _string.lastIndexOf('/');

    return new RegExp(_source, _string.slice(pos+1));
}

module.exports.cloneRegExp = cloneRegExp;

test01.js

var u = require('cloneRegExp');

var reg1  = /abd/;
var reg1c = u.cloneRegExp(reg1);
console.log(reg1);
console.log(reg1c);

var reg2  = /abd/ig;
var reg2c = u.cloneRegExp(reg2);
console.log(reg2);
console.log(reg2c);

test02.js

var u = require('cloneRegExp');

var reg = /<a(?:.*?)href="([^\"]+)"(?:.*?)>(.*?)<\/a>/im;
var reg_cop = u.cloneRegExp(reg);

function test (str) {
    console.log(reg.test(str));
    console.log(reg_cop.test(str));
}

function match (str) {
    var res  = str.match(reg);
    console.log(res);
    var res2 = str.match(reg_cop);
    console.log(res2);
}

[
    '<a href="/hoge.org/hoge">hoge1</a>'
,   '<a title="hoge2" href="/hoge.org/hoge2">hoge2</a>'
,   '<a href="/hoge.org/hoge3" title="done">hoge3</a>'
].forEach(function (str, i) {
    console.log('test %d', i + 1);
    test(str);
    match(str);
    console.log();
});

/* result
test 1
true
true
[ '<a href="/hoge.org/hoge">hoge1</a>',
  '/hoge.org/hoge',
  'hoge1',
  index: 0,
  input: '<a href="/hoge.org/hoge">hoge1</a>' ]
[ '<a href="/hoge.org/hoge">hoge1</a>',
  '/hoge.org/hoge',
  'hoge1',
  index: 0,
  input: '<a href="/hoge.org/hoge">hoge1</a>' ]

test 2
true
true
[ '<a title="hoge2" href="/hoge.org/hoge2">hoge2</a>',
  '/hoge.org/hoge2',
  'hoge2',
  index: 0,
  input: '<a title="hoge2" href="/hoge.org/hoge2">hoge2</a>' ]
[ '<a title="hoge2" href="/hoge.org/hoge2">hoge2</a>',
  '/hoge.org/hoge2',
  'hoge2',
  index: 0,
  input: '<a title="hoge2" href="/hoge.org/hoge2">hoge2</a>' ]

test 3
true
true
[ '<a href="/hoge.org/hoge3" title="done">hoge3</a>',
  '/hoge.org/hoge3',
  'hoge3',
  index: 0,
  input: '<a href="/hoge.org/hoge3" title="done">hoge3</a>' ]
[ '<a href="/hoge.org/hoge3" title="done">hoge3</a>',
  '/hoge.org/hoge3',
  'hoge3',
  index: 0,
  input: '<a href="/hoge.org/hoge3" title="done">hoge3</a>' ]

*/