validate.js

   function validate(){


        var a = false;
        //reset
        var pictureER = document.getElementById("pictureER");
        pictureER.innerHTML = "";
        var userER = document.getElementById("userER");
        userER.innerHTML = "";
        var passER = document.getElementById("passER");
        passER.innerHTML = "";
        var fnameER = document.getElementById("fnameER");
        fnameER.innerHTML = "";
        var lnameER = document.getElementById("lnameER");
        lnameER.innerHTML = "";
        var questionER = document.getElementById("questionER");
        questionER.innerHTML = "";
        var ansER = document.getElementById("ansER");
        ansER.innerHTML = "";
        var emailER = document.getElementById("emailER");
        emailER.innerHTML = "";
        var telER = document.getElementById("telER");
        telER.innerHTML = "";

        var username = ((document.getElementById( "username" )||{}).value)||"";
        var password = ((document.getElementById( "password" )||{}).value)||"";
        var repassword = ((document.getElementById( "repassword" )||{}).value)||"";
        var firstname = ((document.getElementById( "fname" )||{}).value)||"";
        var lastname = ((document.getElementById( "lname" )||{}).value)||"";
        var question = ((document.getElementById( "question" )||{}).value)||"";
        var answer = ((document.getElementById( "answer" )||{}).value)||"";
        // var birthdate = ((document.getElementById( "birthdate" )||{}).value)||"";
        var email = ((document.getElementById( "email" )||{}).value)||"";
        var tel = ((document.getElementById( "tel" )||{}).value)||"";


        //image size
        var profile_pic = document.getElementById("user_picture_file").files[0]; // <input type="file" id="fileUpload" accept=".jpg,.png,.gif,.jpeg"/>
        var profile_pic_name = document.getElementById("user_picture_file").files[0].name;

        if(profile_pic){
            if (profile_pic.size > 5242880) // 2 mb for bytes.
            {
                console.log(profile_pic.size);
                pictureER.innerHTML = "The maximum image size is 5MB";

            }else{
                $.ajax({
                type: "POST",
                url: "picture_exist.php",
                data: ({profile_pic_name:profile_pic_name}),
                success: function(html){
                $("#pictureER").html(html);
                }
            }
        }

        //image type
         var allowedExtension = ['jpeg', 'jpg'];
            var fileExtension = document.getElementById('user_picture_file').value.split('.').pop().toLowerCase();
            var isValidFile = false;

                for(var index in allowedExtension) {

                    if(fileExtension === allowedExtension[index]) {
                        isValidFile = true;
                        break;
                    }
                }

                if(!isValidFile) {
                    if(!pictureER.innerHTML){
                        pictureER.innerHTML = "";
                    }else
                        pictureER.innerHTML += "</br>Please upload file in JPG or jpeg";
                }

        //username
        if( username.length == 0 )
        {
        userER.innerHTML = "Please fill in your username. ";
        }else if( username.length > 20){
        userER.innerHTML = "Your username should be less than 20 characters";
        }
        else{
            console.log("ssss");
            $.ajax({
            type: "POST",
            url: "username_check.php",
            data: "username="+ username ,
            success: function(html){
            $("#userER").html(html);
            }
            });
        }

        //password : have atleast 4, atmost 10
        var passw = /^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,12}$/;
        if( password.length ==0)
        {
        passER.innerHTML = "Please fill in your password. ";
        }else if(password.length <8 || password.length >12  ){
        passER.innerHTML = "Your password have to be between 8 to 12 characters";
        }


        //repassword : must be the same as password
        if( repassword.length == 0 )
        {
        repassER.innerHTML = "Please confirm your password ";
        }else{
            $("#repassword").keyup(validatePassword());
        }

        function validatePassword() {
            var password = $("#password").val();
            var repassword = $("#repassword").val();

            if(password != repassword) {
               repassER.innerHTML = "Your password is not match ";
            }
        }

        //firstname
        if( firstname.length == 0 )
        {
        fnameER.innerHTML = "Please fill in your firstname. ";
        }else if( firstname.length > 20){
        fnameER.innerHTML = "Your name should be less than 20 characters";
        }

        //lastname
        if( lastname.length == 0 )
        {
        lnameER.innerHTML = "Please fill in your lastname. ";
        }else if( lastname.length > 30){
        lnameER.innerHTML = "Your lastname should be less than 30 characters";
        }

        //question
        if( question.length == 0 )
        {
        questionER.innerHTML = "Please fill in your question.";
        }else if(question.length > 80){
        questionER.innerHTML = "Please fill in your question atmost 50 characters. ";
        }

        //answer
        if( answer.length == 0 )
        {
        ansER.innerHTML = "Please fill in your answer. ";
        }else if(answer.length > 30){
        ansER.innerHTML = "Please fill in your answer atmost 30 charactors. ";
        }

        //birthdate
        // if( birthdate.value )
        // {
        // var error = document.getElementById("ansER");
        // error.innerHTML = "Please fill in your answer. ";
        // }else if(ans.value.length > 30){
        // var error = document.getElementById("questionER");
        // error.innerHTML = "Please fill in your answer atmost 30 charactors. ";

         //email
        var emailFilter= /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;
        var illegalChars= /[\(\)\<\>\,\;\:\\\"\[\]]/ ;
        //var emailFilter = /^[^@]+@[^@.]+\.[^@]*\w\w$/ ;
        if( email.length == 0 )
        {
        emailER.innerHTML = "Please fill in your email. ";
        }else if(!checkemail()){
            emailER.innerHTML = "Please fill in your email in the correct form: abc@chowtime.com ";
        }else{
             $.ajax({
            type: "POST",
            url: "email_check.php",
            data: "email="+ email,
            success: function(html){
            $("#emailER").html(html);
            }
            });
        }

        function checkemail(){
            var emailFilter=/^.+@.+\..{2,3}$/;
            var str=document.frmAdd.email.value;
        if (!(emailFilter.test(str))) {
            return false;
        }
            return true;
        }

        //tel
        function isPhoneNo(input){
            var regExp = /^\(?(\d{2,3})\)?[-. ]?(\d{3,4})[-. ]?([0-9]{4})$/;
            return regExp.test(input);
        }
        if( tel.length == 0 ){
        telER.innerHTML = "Please fill in your phone number. ";
        }else if (!isPhoneNo(tel)) {
        telER.innerHTML = "Please fill in your phone number in the correct format:</br>099-999-3333 or 011 222 3333 or 0884443333. ";

        }

        else{
            a = true;
        }
        return a;
    }