Validation (practical)

It is important to validate any user input before saving it to your backend. With International Telephone Input, there are two options for validation: (1) practical validation (which is more future-proof and suitable for most uses cases), or (2) precise validation. The practical option is to use the isValidNumber method, which is a simple form of validation that only checks the number length, which should be sufficient for most use cases. The advantage of this approach is that it is much more future-proof as while countries around the world regularly update their number rules, they very rarely change their number lengths.

If isValidNumber returns false and you'd like more detail, you can then use the getValidationError method to get more information. This method returns an error code (integer), which you can then map to your own custom error message, as in the example below.

All validation methods require the utils script to be loaded (see the readme for instructions). The utils script contains a custom build of Google's libphonenumber library in JavaScript, which provides validation tools as well as formatting and placeholder number generation.

Markup

<input id="phone" type="tel">
<button class="button" id="btn" type="button">Validate</button>
<span id="valid-msg" class="hide">✓ Valid</span>
<span id="error-msg" class="hide"></span>

Code

const input = document.querySelector("#phone");
const button = document.querySelector("#btn");
const errorMsg = document.querySelector("#error-msg");
const validMsg = document.querySelector("#valid-msg");

// here, the index maps to the error code returned from getValidationError - see readme
const errorMap = ["Invalid number", "Invalid country code", "Too short", "Too long", "Invalid number"];

// initialise plugin
const iti = window.intlTelInput(input, {
  initialCountry: "us",
  utilsScript: "/intl-tel-input/js/utils.js?1730730622316"
});

const reset = () => {
  input.classList.remove("error");
  errorMsg.innerHTML = "";
  errorMsg.classList.add("hide");
  validMsg.classList.add("hide");
};

const showError = (msg) => {
  input.classList.add("error");
  errorMsg.innerHTML = msg;
  errorMsg.classList.remove("hide");
};

// on click button: validate
button.addEventListener('click', () => {
  reset();
  if (!input.value.trim()) {
    showError("Required");
  } else if (iti.isValidNumber()) {
    validMsg.classList.remove("hide");
  } else {
    const errorCode = iti.getValidationError();
    const msg = errorMap[errorCode] || "Invalid number";
    showError(msg);
  }
});

// on keyup / change flag: reset
input.addEventListener('change', reset);
input.addEventListener('keyup', reset);