luhn-generator
Version:
A generator of numbers that passes the validation of Luhn algorithm or Luhn formula, also known as the 'modulus 10' or 'mod 10' algorithm
54 lines (53 loc) • 1.56 kB
JavaScript
var META = require('./_uid')('meta');
var isObject = require('./_is-object');
var has = require('./_has');
var setDesc = require('./_object-dp').f;
var id = 0;
var isExtensible = Object.isExtensible || function () {
return true;
};
var FREEZE = !require('./_fails')(function () {
return isExtensible(Object.preventExtensions({}));
});
var setMeta = function (it) {
setDesc(it, META, { value: {
i: 'O' + ++id, // object ID
w: {} // weak collections IDs
} });
};
var fastKey = function (it, create) {
// return primitive with prefix
if (!isObject(it)) return typeof it == 'symbol' ? it : (typeof it == 'string' ? 'S' : 'P') + it;
if (!has(it, META)) {
// can't set metadata to uncaught frozen object
if (!isExtensible(it)) return 'F';
// not necessary to add metadata
if (!create) return 'E';
// add missing metadata
setMeta(it);
// return object ID
} return it[META].i;
};
var getWeak = function (it, create) {
if (!has(it, META)) {
// can't set metadata to uncaught frozen object
if (!isExtensible(it)) return true;
// not necessary to add metadata
if (!create) return false;
// add missing metadata
setMeta(it);
// return hash weak collections IDs
} return it[META].w;
};
// add metadata on freeze-family methods calling
var onFreeze = function (it) {
if (FREEZE && meta.NEED && isExtensible(it) && !has(it, META)) setMeta(it);
return it;
};
var meta = module.exports = {
KEY: META,
NEED: false,
fastKey: fastKey,
getWeak: getWeak,
onFreeze: onFreeze
};