Form validation (required fields)

Question

JavaScript

This is the first time I've come across such a situation.
Here is a similar form.

<form action='name.php'>
Введите ваше имя: <input name='name' type='name' value='namel' />
Введите email: <input name='email' type='email' value='Не email' /> или
Введите сотовый телефон: <input name='tel1' type='tel' pattern='8[0-9]{10}'/>
<input type='submit' value='Отправить' />

It is necessary that 1 of the fields must be filled in "phone" or "mail"
How to implement this? And you can still validate against incorrect data, xss prevention.
Thank you)

Answer 1

<input name='email' type='email' value='Не email' required='required' />

Answer 2

Well, check for an empty value

if(document.getElementsByName('email')[0].value === ""
    && document.getElementsByName('tel1')[0].value === ""
) {
    alert("Пожалуйста заполните, 'email' или 'telephone'");
}

Answer 3

on jquery with trimming spaces
if (!$.trim($('input[name=email]').val()).length && !$.trim($('input[name=tel1]').val( )).length) {
console.log("Please fill in 'email' or 'telephone'")
}