Credit card prediction in Javascript

I'm writing a tool that onkeydown will run the current value being entered in an input box to check to see if it matches a regex for one of the 4 major types of credit cards.

I feel like it kind of works, but it's flaky so I wanted to figure out what was causing it to give faulty response (eg sometimes it'll output 2 values instead of one). Is it because I need to set a flag variable before looping? Upon match of the correct card, I'm just returning from the loop through the object, so I thought that'd be sufficient enough...

The criteria for the regexes were pulled from this site:

  • Visa : ^4[0-9]{12}(?:[0-9]{3})?$ All Visa card numbers start with a 4. New cards have 16 digits. Old cards have 13.

  • MasterCard : ^5[1-5][0-9]{14}$ All MasterCard numbers start with the numbers 51 through 55. All have 16 digits.

  • American Express : ^3[47][0-9]{13}$ American Express card numbers start with 34 or 37 and have 15 digits.

  • Discover : ^6(?:011|5[0-9]{2})[0-9]{12}$ Discover card numbers begin with 6011 or 65. All have 16 digits.

    $(function() {
    
    var $cardNumber = $('#js-cardnumber');
    
    var ccMap = {};
    
    ccMap.cards = {
        'amex': '^3[47][0-9]{13}$',
        'discover': '^6(?:011|5[0-9]{2})[0-9]{12}$',
        'mastercard': '^5[1-5][0-9]{14}$',
        'visa': '^4[0-9]{12}(?:[0-9]{3})?$'
    };
    
    
    $cardNumber.keydown(function() {
    for (var cardType in ccMap.cards) {
        if (ccMap.cards.hasOwnProperty(cardType)) {
            var regex = ccMap.cards[cardType];
            if (regex.match($(this).val())) {
                console.log(cardType);
                return;
            }
        }
    }
    });
    });​
    
  • Here's a fiddle


    It seems like you're using the regular expressions in a wrong way.

    If you want to check a string against a regular expression, you can use the match() method of the string:

    string.match(regexp) // returns boolean
    

    You're doing it the wrong way:

    if ( regex.match($(this).val()) ) {
    

    tries to interpret the current value as a regular expression. Must be this way:

    if ( $(this).val().match(regex) ) {
    

    You can also cache the regular expressions to make your script more efficient:

    ccMap.cards = {
        'amex': /^3[47][0-9]{13}$/,  // store an actual regexp object, not a string
        // ...
    
    // The way you test changes, now you're able to use the "test"
    // method of the regexp object:
    if ( regex.test($(this).val()) ) {
    
    链接地址: http://www.djcxy.com/p/70724.html

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