HTMLInputElement: checkValidity() method
The checkValidity() method of the HTMLInputElement interface returns a boolean value which indicates if the element meets any constraint validation rules applied to it. If false, the method also fires an invalid event on the element. Because there's no default browser behavior for checkValidity(), canceling this invalid event has no effect.
Note:
An HTML <input> element with a non-null validationMessage is considered invalid, will match the CSS :invalid pseudo-class, and will cause checkValidity() to return false. Use the HTMLInputElement.setCustomValidity() method to set the HTMLInputElement.validationMessage to the empty string to set the validity state to be valid.
Syntax
checkValidity()
Parameters
None.
Return value
Returns true if the element's value has no validity problems; otherwise, returns false.
Examples
HTML
We include a form containing a required number field and two buttons: one to check the form and the other to submit it.
<form action="#" method="post">
<p>
<label for="age">Your (21 to 65) </label>
<input type="number" name="age" required id="age" min="21" max="65" />
</p>
<p>
<button type="submit">Submit</button>
<button type="button" id="check">checkValidity()</button>
</p>
<p id="log"></p>
</form>
JavaScript
const output = document.querySelector("#log");
const checkButton = document.querySelector("#check");
const ageInput = document.querySelector("#age");
ageInput.addEventListener("invalid", () => {
console.log("Invalid event fired.");
});
checkButton.addEventListener("click", () => {
const checkVal = ageInput.checkValidity();
output.innerHTML = `checkValidity returned: ${checkVal}`;
});
Results
When false, if the value is missing, below 21, above 65, or otherwise invalid, the invalid event will be logged to the console. To report the error to the user, use HTMLInputElement.reportValidity() instead.