IPv6 abbreviation

abbreviateIpv6.js

function abbreviateIpv6(ip) {
    var out = ip.replace(/(^|\:)0{1,3}([0-9]+)/g, "$1$2");
    out = out.replace(/0(\:0)+/, ":");
    out = out.replace(/\:{3,}/g, "::");
    if (out === ":") {
        out = "::";
    }

    return out;
}

abbreviateIpv6.spec.js

describe('To abbreviate IPv6 addresses.', function () {
    it('should abbreviate IPv6 addresses', function () {
        expect(abbreviateIpv6('2001:0000:0111:0000:0011:0000:0001:0000')).toBe('2001:0:111:0:11:0:1:0');
        expect(abbreviateIpv6('0000:0000:0111:0000:0011:0000:0001:0000')).toBe('::111:0:11:0:1:0');
        expect(abbreviateIpv6('2001:0000:0111:0000:0011:0001:0000:0000')).toBe('2001:0:111:0:11:1::');
        expect(abbreviateIpv6('2001:0000:0111:0000:0011:0000:0001:0000')).toBe('2001:0:111:0:11:0:1:0');
        expect(abbreviateIpv6('2001:0001:0000:0001:0000:0000:0000:0001')).toBe('2001:1:0:1::1');
        expect(abbreviateIpv6('2001:0001:0000:0001:0000:0000:0000:0000')).toBe('2001:1:0:1::');
        expect(abbreviateIpv6('0000:0000:0000:0000:0000:0000:0000:0000')).toBe('::');
        expect(abbreviateIpv6('0000:0000:0000:0000:0000:0000:0000:0001')).toBe('::1');
        expect(abbreviateIpv6('0000:0000:0000:0001:0000:0000:0000:0001')).toBe('::1:0:0:0:1');
        expect(abbreviateIpv6('0000:0000:0001:0000:0000:0001:0000:0000')).toBe('::1:0:0:1:0:0');
        expect(abbreviateIpv6('2041:0000:140F:0000:0000:0000:875B:131B')).toBe('2041:0:140F::875B:131B');
        expect(abbreviateIpv6('2001:0001:0002:0003:0004:0005:0006:0007')).toBe('2001:1:2:3:4:5:6:7');
        expect(abbreviateIpv6('2001:0000:0000:0000:1111:0000:0000:0000')).toBe('2001::1111:0:0:0');
        expect(abbreviateIpv6('2001:db8:0:0:0:0:2:1')).toBe('2001:db8::2:1');
    });
});