Question

I have the following regex test on a users input:

function validate_form() {

return /^[a-fA-F0-9]+$/.test(document.form.input.value);

}

I the users input failed to meet the criteria, then how would i get an alert put in this code to inform them?

Answer 1

You could replace the return statement with:

var isValid = /^[a-fA-F0-9]+$/.test(document.form.input.value);
if (!isValid) alert("Your value was invalid.");
return isValid;

Alternatively, you could keep your validation function as above, and do:

if (!validate_form()) alert("Your value was invalid.");

If you want to show the error message in the document itself, then you could do something like, and replace alert() above with error():

function error(message) {
  document.getElementById("error").innerHTML = message;
}

This assumes that you have an element in your HTML with id="error" e.g.:

<div id="error"></div>