Not sure what exactly this has to do with validation, but this is not how you set a value to a form element in jQuery:

$("#guestForm-email").value = "[email protected]"

This is:

$("#guestForm-email").val("[email protected]")

First of all you cant write this as

$("#guestForm-email").value = "[email protected]"

this is the correct syntax

$("#guestForm-email").val("[email protected]")

and try to do this in function that return true if the data is valid an call it in

<form onSubmit="return validate()">

I guess what you are trying to do is to validate the e-mail sent on the input text field using jQuery. You can use a reg expression for this within your button’s click event handler like so:

$(document).ready(function() {
    $("button[type=submit]").click(function() {
        if(/^w+([.-]?w+)*@w+([.-]?w+)*(.w{2,3})+$/.test($("#guestForm-email").value)) {
            return $("#guestForm-email").value;
        } else {
            alert("Invalid E-mail");
        }
    }
}

I think you want to append text inside input:

$("#guestForm-email").val($("#guestForm-email").val()+"[email protected]")

Here is the code;

<form data-test="loginForm-container" novalidate="" method="POST" enctype="multipart/form-data">
<div class="css-o5d3v1 e1ovefus2">
    <div data-test="guestForm-email-wrapper" class="e1ovefus1 css-yjv4po e1eu3ser1">
        <div class="css-gg4vpm e1eu3ser4">
            <label for="guestForm-email" id="guestForm-email-label" data-test="input-label" class="css-1k1vx4d e1eu3ser5">Email Address*</label>
        </div>
        <div class="css-1tpy6sb e1eu3ser7">
            <input data-test="guestForm-email" aria-invalid="true" aria-required="true" id="guestForm-email" type="email" name="email" aria-labelledby="guestForm-email-label" class="css-15uq4zo e1eu3ser9" value="" aria-describedby="guestForm-email-error">
        </div><span data-test="input-error" id="guestForm-email-error" role="alert" class="css-mf5akt e1eu3ser0">Please enter email address</span></div>
</div>
<button type="submit" data-test="guestForm-submitButton" class="e1ovefus0 css-1wqqz58 e1y6awi20"><span>Continue as Guest</span></button>

I tried doing;

$("#guestForm-email").value = "[email protected]"

but when submit it deletes the text in textfield.

I just need to learn how to validate it in JQUERY.

Can anyone help?

Thanks.