<!-- Allowed file script start -->
		function validateFileType(){
			var fileName = document.getElementById("actual-btn").value;
			var idxDot = fileName.lastIndexOf(".") + 1;
			var extFile = fileName.substr(idxDot, fileName.length).toLowerCase();
			if (extFile=="jpg" || extFile=="jpeg" || extFile=="png" || extFile=="pdf"){
				//TO DO
			}else{
				alert("Only jpg, jpeg, png and pdf files are allowed!");
			}   
		}


		var fileName = document.getElementById('actual-btn').value.toLowerCase();
if(!fileName.endsWith('.jpeg') && !fileName.endsWith('.jpg') && !fileName.endsWith('.png') && !fileName.endsWith('.pdf')){
    alert('Please upload jpeg, jpg, png, pdf files only.');
    return false;
}
	<!-- Allowed file script end -->

<!-- file script -->
<script>
	const actualBtn = document.getElementById('actual-btn');

const fileChosen = document.getElementById('file-chosen');

actualBtn.addEventListener('change', function(){
  fileChosen.textContent = this.files[0].name
})

<!-- The `multiple` attribute lets users select multiple files. -->
  const fileSelector = document.getElementById('actual-btn');
  fileSelector.addEventListener('change', (event) => {
    const fileList = event.target.files;
    console.log(fileList);
  });