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:
Most of us carry credit cards and ATM cards. These, typically, have sixteen digits on the front. These digits are the unique account number for the card. For obvious reasons, just any sixteen digits will not work, they follow pattern.Here's a fictitious card I made up: The first few characters of the card number describe the type of card.redit card numbers are often typed in, input, transferred and quoted. All of this transmission can cause errors, especially considering that humans are involved. Humans often make mistakes in transferal. To try and minimize this, credit card numbers contain a check digit.