How can I validate an email address in JavaScript?

To validate an email address in JavaScript, you can use a regular expression to test whether the given string is a valid email address. Here’s an example of how you can do this:

function isValidEmail(email) {
  var re = /^(([^<>()[\]\\.,;:\s@\"]+(\.[^<>()[\]\\.,;:\s@\"]+)*)|(\".+\"))@((\[[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\.[0-9]{1,3}\])|(([a-zA-Z\-0-9]+\.)+[a-zA-Z]{2,}))$/;
  return re.test(email);
}

This function defines a regular expression that matches a valid email address, and uses the test method to test whether the given string is a valid email address.

You can then use this function to validate an email address like this:

if (isValidEmail(email)) {
  // email is valid
} else {
  // email is invalid
}

Keep in mind that this regular expression is just one way to validate an email address, and it may not catch every possible invalid email address. It’s always a good idea to also check for other constraints, such as the length of the email address and the presence of certain characters.