How to validate Maximum Size upload file?

<input type="file" id="file_upload" name="file_upload" class="form-control" onchange="Validatefile(this.id,this.value)" >
<span class="required" aria-required="true">(Only PDF,JPG,PNG files are allowed, File Size Allowed 5MB)</span>
<span class="required" id="file_upload_error" aria-required="true"></span>


<script>
function Validatefile(id,val){

var image =$('#'+id).val();

if(image!=''){

var checkimg = image.toLowerCase();
if (!checkimg.match(/(\.jpg|\.png|\.JPG|\.PNG|\.jpeg|\.JPEG|\.pdf)$/)){
$('#'+id).focus();
alert("Invalid file extension, Only jpg,jpeg,png,bmp,pdf files are Allowed");
$('#'+id).val('');
return false;
}
var img = document.getElementById(id);
var fsize=img.files[0].size;
const file = Math.round((fsize / 1024));
if(file >= 5000) {
alert("File size too large, Please select a file less than 5mb");
$('#'+id).val("");
return false;
}
return true;




}
}
</script>