This is the piece of code I'd like to refactor. Basically, when the credit card option is selected, then do I want the credit card number, zip code, and Cvv inputs to be validated.

validateForm=(e)=> {
  Array.from(inputElements).forEach(element=> {
    let value=element.value;
    let input=element;
    if (input===name) {
      errorMessage(isValidName, input, value, e)
    } else if (element===email) {
      errorMessage(isValidEmail, input, value, e);
    } else if (element===creditNumber) {
      if (creditOptionChecked()) {
        errorMessage(isValidCreditCard, input, value, e);
    } else if (element===zip) {
      if (creditOptionChecked()) {
        errorMessage(isValidZipCode, input, value, e);
    } else if (element===cvv) {
      if (creditOptionChecked()) {
        errorMessage(isValidCvv, input, value, e);
    } else if (element==fieldSetActivity) {

form.addEventListener('submit', (e)=> {

I've been at this for a couple hours, but I'm still a bit new to be able to implement something that is modular. Here is a link to my JS fiddle, so you can see the rest of the javascript code: https://jsfiddle.net/apasric4/4xfL9utv/2/


1 Answer 1


Incomplete code

Your question's code is missing so much information there is not much to review.

Because of this I can only review the code in regard to exactly the logic your function performs.

Style points

  • Don't add code that is not needed. Eg

    • The variable input is a copy of element having two names for the same reference will lead to confusion, mistakes and bugs.

    • You add a function to form submit, and all it does is call validateForm. Set the listener to validateForm eg form.addEventListener('submit', validateForm) and avoid the middle man.

  • Good code does not repeat AKA is DRY (Don't Repeat Yourself).

    Examples of repeated code;

    • You call errorMessage, with the same 3 last arguments five times. Create a function and just pass the first argument, let the function call errorMessage with the rest of the arguments.

    • You repeat the same statement if (creditOptionChecked()) { three times. Again hand the repetitive source code to a function..

  • Variables that do not change and/or should not change should be declared as constants. eg const value = element.value; rather than let value = element.value;

  • Array.from requires an array like argument. Array like arguments are all iterable thus you do not need to create an array before you iterate. The line Array.from(inputElements).forEach(element=> { can be written as inputElements.forEach(element => { or for (const element of inputElements) {

    Array iterators (example Array.forEach) are not as efficient as for or while loops. Using for or while loops when you can also gives you a better sense of the code complexity, while using a little less memory and power.


Rewriting your function to be compatible with the original under all possible unknown states using the above points.

form.addEventListener("submit", e => {
    var input;
    const error = valid => errorMessage(valid, input, input.value, e);
    const optError = valid => creditOptionChecked() && error(valid);
    for (input of inputElements) {
        if (input === name) { error(isValidName) }
        else if (input === email) { error(isValidEmail) }
        else if (input === creditNumber) { optError(isValidCreditCard) }
        else if (input === zip) { optError(isValidZipCode) }
        else if (input === cvv) { optError(isValidCvv) }
        else if (input == fieldSetActivity) { validateCheckboxes(e) }

There are some improvements that can be made depending on the unknowns, maybe needing no if statements at all, but I likely waste both of our times if I speculate.


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