isAmericanExpress

isAmericanExpress :: a → Boolean

Reports whether the received value is a valid credit card number and is an American Express card

import isAmericanExpress from 'deep-waters/credit-cards/isAmericanExpress';

isAmericanExpress(347190259623701); // American Express → true

isAmericanExpress(4286124395547263); // VISA → false
isAmericanExpress(6011583945260254); // Discover → false
isAmericanExpress(38716394960899); // Diners Club → false
isAmericanExpress(3528701379615495); // JCB → false
isAmericanExpress('6011-5839-4526-0254'); // Credit card format → false
isAmericanExpress("foo"); // → false
isAmericanExpress(undefined); // → false

Please note, isAmericanExpress assumes the receiving value is a number or a string without the usual dashes. It only evaluates the credit card number, not its format.