Getting a country dialling/calling code for a phone number

get-country-code.js

var codes = [1,7,20,27,30,31,32,33,34,36,39,40,41,43,44,45,46,47,48,49,51,52,
    53,54,55,56,57,58,60,61,62,63,64,65,66,81,82,84,86,90,91,92,93,94,95,98,
    211,212,213,216,218,220,221,222,223,224,225,226,227,228,229,230,231,232,
    233,234,235,236,237,238,239,240,241,242,243,244,245,246,248,249,250,251,
    252,253,254,255,256,257,258,260,261,262,263,264,265,266,267,268,269,290,
    291,297,298,299,350,351,352,353,354,355,356,357,358,359,370,371,372,373,
    374,375,376,377,378,380,381,382,385,386,387,389,420,421,423,500,501,502,
    503,504,505,506,507,508,509,590,591,592,593,594,595,596,597,598,599,670,
    672,673,674,675,676,677,678,679,680,681,682,683,685,686,687,688,689,690,
    691,692,850,852,853,855,856,870,880,886,960,961,962,963,964,965,966,967,
    968,970,971,972,973,974,975,976,977,992,993,994,995,996,998];

var strip = function (num) {
    return num.toString().trim().replace(/[^0-9]/g, "");
};

var getCountryCode = function (num) {
    num = strip(num);
    var i = 1, code;

    while (codes.indexOf(code) === -1 && i <= num.length) {
        code = parseInt(num.slice(0, i), 10);
        i += 1;
    }

    return (code.length !== num.length) ? code : null;
};

console.log(getCountryCode(447123456789));