luci/applications/luci-app-dockerman/luasrc/view/dockerman/images_load.htm

<div style="display: inline-block;">
	<input type="button"" class="btn cbi-button cbi-button-add" id="btnload" name="load" value="<%:Load%>" />
	<input type="file" id="file_load" style="visibility:hidden; position: absolute;top: 0px; left: 0px;" accept="application/x-tar" />
</div>
<script>
	let btnLoad = document.getElementById('btnload')
	btnLoad.onclick = function (e) {
		document.getElementById("file_load").click()
		e.preventDefault()
	}

	let fileLoad = document.getElementById('file_load')
	fileLoad.onchange = function(e){
		let fileLoad = document.getElementById('file_load')
		if (!fileLoad.value) {
			return
		}
		let fileName = fileLoad.files[0].name
		let formData = new FormData()
		formData.append('upload-filename', fileName)
		formData.append('upload-archive', fileLoad.files[0])
		let xhr = new XMLHttpRequest()
		uci_confirm_docker()
		xhr.open("POST", '<%=luci.dispatcher.build_url("admin/docker/images_load")%>', true)
		xhr.onload = function() {
			location.reload()
		}
	xhr.send(formData)
	}
</script>