Answer 1

Error handling is the process of responding to the occurrence of errors.

It is very similar in both JS and PHP.
You can handle errors with try-catch.

PHP:
try {
$name = $_POST["name"];
} catch (Exception $e) {
echo $e->getCode();
echo $e->getMessage();
}

JS:
try {
let name = document.querySelector("#name");
} catch (exception) {
document.querySelector("#error").textContent = "An error occured!";
}