Input file test
by ktsn
HTML
<div>
File Size: <output id="size"></output>
</div>
<input id="file" type="file">
JavaScript
const input = document.getElementById('file')
input.addEventListener('change', event => {
const file = event.target.files[0]
const el = document.getElementById('size')
el.textContent = (file.size / 1024 / 1024) + ' MB'
})