credit cards validation using javascript and Luhn algorithm
Lets use a randomly generated Visa credit card number 4539300916139765
Step 1 : Remove the last number from the credit card number | 4 5 3 9 3 0 0 9 1 6 1 3 9 7 6
Step 2 : Reverse the numbers | 6 7 9 3 1 6 1 9 0 0 3 9 3 5 4
Step 3 : Multiply each odd number | 12 7 18 3 2 6 2 9 0 0 6 9 6 5 8
Step 4 : Each number over 9 needs to be subtracted by 9 | 3 7 9 3 2 6 2 9 0 0 6 9 6 5 8
Step 5 : Count all numbers together | 75
Step 6 : Add the last digit of the credit card (5) with the total sum (75) | 80
Step 7 : If the digit you have is a multiple of 10 than the credit card is valid 8 * 10 is 80
Card Start with 4 : VISA 16 digit Card Start with 5 : Master 16 digit Card Start with 3 : MX 15 digit