There are two factors to consider when deciding how to handle the problem of a work sample: sample size and population characteristics. Sample size is determined by a formula based on the power of the sample or its ability to represent the population with a predictable margin of error.
The resulting complexity makes card type detection code difficult to write, read, and maintain. As an example of this complexity, consider this JavaScript regular expression used to detect Discover card numbers starting with 6011, 622126-622925, 644-649, and 65:
Generally, the first number or two of a credit or debit signifies the card provider, followed by digits that determine everything from the currency being used, to the bank processing the transaction, to the individual's account number.merican Express. fonalite | FonalitÃ© Flickr American express uses the first two numbers of the card to identify. Itself that-two digit number will be either 34 or. 37 the third and fourth digit signify the type of card and the currency being, used according To Clearpoint Credit. counseling