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Edit File: ajax_jquery.js

$(document).ready(function(){

$("#reloadCaptcha").click(function(){
    $("#captchaImage").attr("src","captcha.php?"+Date.now());
});

$("#contactForm").submit(function(e){
        e.preventDefault();

$(".text-danger").html(""); // clear errors

let valid = true;

let name = $("#name").val().trim();
        let email = $("#email").val().trim();
        let phone = $("#phone_number").val().trim();
        let message = $("#message").val().trim();
        let captcha = $("#captcha").val().trim();

// NAME
        if(name === ""){
            $(".name-error").html("Name is required");
            valid = false;
        }

// EMAIL
        let emailPattern = /^[^ ]+@[^ ]+\.[a-z]{2,3}$/;
        if(!email.match(emailPattern)){
            $(".email-error").html("Valid email required");
            valid = false;
        }

// PHONE
        if(!/^[0-9]{10}$/.test(phone)){
            $(".number-error").html("Enter 10 digit mobile number");
            valid = false;
        }

// MESSAGE
        if(message === ""){
            $(".message-error").html("Message required");
            valid = false;
        }

// CAPTCHA
        if(captcha === ""){
            $(".captcha-error").html("Enter captcha");
            valid = false;
        }

if(!valid) return;

// AJAX
        $.ajax({
            url: "form_validaion.php",
            method: "POST",
            data: $(this).serialize(),
            success: function(response){
                $("#mail-status").html(response);
                $("#contactForm")[0].reset();

// reload captcha after submit
                $("#captchaImage").attr("src", "captcha.php?" + Date.now());
            }
        });

});