Next.JS custom form validation not working – ReactJS

I have a contact page, and I am trying to validate the form. When page is refreshed and I click on submit button then only the last element’s error is generated, it should generate error for every input according to validation.
Screenshot of form issue
Form validation is working perfect with onChange event. But it doesn’t work fine when page is refreshed and I click on submit button without putting values to inputs.
Here is my code:

import { useState } from "react";

function ContactForm() {

    const [fields, setFields] = useState({});
    const [errors, setErrors] = useState({});
    const [formValid, setFormValid] = useState(false);

    async function handleOnSubmit(e) {
        e.preventDefault();

        console.log('fields', fields);
        console.log('errors', errors);
        console.log('formValid', formValid);

        const formData = {};
        [...e.currentTarget.elements].map((field) => {
            if (!field.name) return false;
            checkValidation([field.name], field.value);
            setFields({...fields, [field.name]: field.value});
        });

        if (formValid === false) return false;

        try {
            const response = await fetch('/api/mail', {
                                method: 'post',
                                body: JSON.stringify(formData)
                            });
            const body = await response.json();
            console.log(body);
        } catch (error) {
            console.log(error);
        }

        console.log(formData);
    }

    function handleValidation(e) {
        const name = e.target.name;
        const value = e.target.value;
        checkValidation(name, value);
    }

    function checkValidation(name, value) {
        if (value === "") {
            delete fields[name];
            setErrors({...errors, [name]: 'Required'});
            setFormValid(false);
            return false;
        }

        delete errors[name];
        setFields({...fields, [name]: value});
        setFormValid(true);
        // Special validation for email
        emailValidation(name, value);

        console.log('fields on validaton', fields);
        console.log('errors on validation', errors);
    }

    // Email Validation
    function emailValidation(name, value) {
        const emailRegex = new RegExp(/[a-z0-9._%+-]+@[a-z0-9.-]+.[a-z]{2,15}/g);
        if ((name == 'email') && (emailRegex.test(value) === false)) {
            delete fields[name];
            setErrors({...errors, [name]: 'Email is not validate'});
            setFormValid(false);
        }
    }

    return (
        <div className="mt-5 mt-md-0">
            <h1 className="section-title h1-responsive text-center mb-4">
                <span>
                    Contact Us
                    <svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 456.99 38"><defs><style dangerouslySetInnerHTML={{__html: ".cls-1{fill:#cb0a34;}" }} /></defs><title>latest from out videos</title><g id="Layer_2" data-name="Layer 2"><g id="Layer_1-2" data-name="Layer 1"><path className="cls-1" d="M456.28,8.29a4.6,4.6,0,0,0,.29-.59c0-.11.08-.21.11-.31a4.56,4.56,0,0,0,.21-.72l0-.21A6.11,6.11,0,0,0,457,5.6h0a5.5,5.5,0,1,0-9.24,4C422.6,9.89,288,9.52,281.13,9.52h-31c-7.86,0-15.13,2.18-21.14,7.26a30.14,30.14,0,0,0-8.72-5.25c-4.68-1.82-9.42-2-14.32-2H9.24A5.5,5.5,0,1,0,0,5.5v0c0,.05,0,.09,0,.14a3.4,3.4,0,0,0,0,.45c0,.12,0,.23,0,.35l.06.3A1.82,1.82,0,0,0,.22,7,5.48,5.48,0,0,0,4.5,10.9a5.13,5.13,0,0,0,1.12.16c.85,0,1.7,0,2.54,0H209.44a28.85,28.85,0,0,1,19,7.26,28.31,28.31,0,0,0-6.38,9.13L229,38.29,236,27.45h0a28.11,28.11,0,0,0-6.38-9.12A28.8,28.8,0,0,1,241.09,12c4-1.09,8-1,12.14-1H451l.54,0a5.47,5.47,0,0,0,3.21-1l.07,0s0,0,.05-.05a4.53,4.53,0,0,0,.62-.54l.24-.26a6.41,6.41,0,0,0,.39-.52C456.15,8.52,456.21,8.4,456.28,8.29Z" /></g></g></svg>
                </span>
            </h1>
            <form className="contact_form" method="post" onSubmit={handleOnSubmit}>
                <div className="response-status"></div>
                <div className="form-group row">
                    <div className="col-md-6 mb-2">
                        <label className="mb-1">Name <span className="text-danger">*</span></label>
                        <input
                            type="text"
                            name="name"
                            className={`form-control ${errors.name ? 'is-invalid' : ''}`}
                            onChange={handleValidation}
                        />
                        {errors.name && <span className="text-danger">{errors.name}</span>}
                    </div>
                    <div className="col-md-6 mb-2">
                        <label className="mb-1">Email <span className="text-danger">*</span></label>
                        <input
                            type="text"
                            name="email"
                            className={`form-control ${errors.email ? 'is-invalid' : ''}`}
                            onChange={handleValidation}
                        />
                        {errors.email && <span className="text-danger">{errors.email}</span>}
                    </div>
                    <div className="col-md-12 mb-2">
                        <label className="mb-1">Subject:</label>
                        <input type="text" name="subject" className="form-control" />
                    </div>
                    <div className="col-md-12 mb-3">
                        <label className="mb-1">Message <span className="text-danger">*</span></label>
                        <textarea
                            name="message"
                            className={`form-control ${errors.message ? 'is-invalid' : ''}`}
                            rows="5"
                            onChange={handleValidation}
                        ></textarea>
                        {errors.message && <span className="text-danger">{errors.message}</span>}
                    </div>
                    <div className="col-md-12">
                        <button type="submit" className="btn btn-primary btn-block rounded waves-effect waves-light">Send Message</button>
                    </div>
                </div>
            </form>
        </div>
    )
}

export default ContactForm

I don’t know why it is not working fine. Please check the code. I can’t find the issue in my code, I am stuck.