This code snippet will check if both email field matched or not.

email_match_check.js

let emailFieldOne = document.getElementById('ff_156_email');
let emailFieldTwo = document.getElementById('ff_156_email_1');
let submitButton = document.querySelector('.ff-btn-submit');
submitButton.style.display = 'none';

emailFieldTwo.insertAdjacentHTML('afterend', '<div id="customDiv" style="text-align:center; display:none; color:red;"></div>');

let displayed = false;

let customDiv = document.getElementById('customDiv');

emailFieldTwo.addEventListener('blur', function(){
    if(emailFieldTwo.value != emailFieldOne.value){
        if(!displayed){
            displayed = true;
            customDiv.style.display = 'block';
        }
        customDiv.innerHTML = 'Email does not matched';
        submitButton.style.display = 'none';
    }else{
        displayed = false;
        customDiv.style.display = 'none';
        submitButton.style.display = 'block';
    }
});