FormData Size

HTML

<form>
<input name=a>
<input type=file name=b>
<button type=button>Get Size</button>
</form>

JavaScript

$('button').on('click', function(){
	var fd = new FormData(this.form);
  console.log(fd.entries());
  var size = 0;
  for(var pair of fd.entries()) {
    if (pair[1] instanceof Blob) 
      size += pair[1].size;
    else
      size += pair[1].length;
  }
  alert(size+' '+fd.length)
})