luhn-generator
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A generator of numbers that passes the validation of Luhn algorithm or Luhn formula, also known as the 'modulus 10' or 'mod 10' algorithm
36 lines (31 loc) • 952 B
JavaScript
/** Used as references for various `Number` constants. */
var MAX_SAFE_INTEGER = 9007199254740991;
/* Built-in method references for those with the same name as other `lodash` methods. */
var nativeFloor = Math.floor;
/**
* The base implementation of `_.repeat` which doesn't coerce arguments.
*
* @private
* @param {string} string The string to repeat.
* @param {number} n The number of times to repeat the string.
* @returns {string} Returns the repeated string.
*/
function baseRepeat(string, n) {
var result = '';
if (!string || n < 1 || n > MAX_SAFE_INTEGER) {
return result;
}
// Leverage the exponentiation by squaring algorithm for a faster repeat.
// See https://en.wikipedia.org/wiki/Exponentiation_by_squaring for more details.
do {
if (n % 2) {
result += string;
}
n = nativeFloor(n / 2);
if (n) {
string += string;
}
} while (n);
return result;
}
module.exports = baseRepeat;