map.js

module.exports = {
	"0000fee0-0000-1000-8000-00805f9b34fb": {
		"0000ff05-0000-1000-8000-00805f9b34fb": function(char) {
			return char.writeValue(new Uint8Array([
				0x12,
				0x01,
			])).then(console.log).catch(console.log)
		},
		"0000ff0e-0000-1000-8000-00805f9b34fb": function(char) {
			char.addEventListener("characteristicvaluechanged", function(event) {
				let self = new Int16Array(this.value.buffer)
				console.log(JSON.stringify(self))
			})
			char.startNotifications().then(function(result) {
				console.log(result)
			})
			char.writeValue(new Uint8Array([ 1, ])).then(function(res) {
				return res
			})
		},
	},
}

webbt.js

function ble(map, cleanup) {
	return navigator.bluetooth.requestDevice({
		optionalServices: Object.keys(map),
		acceptAllDevices: true,
	}).then(function(device) {
		device.gatt.connect().then(function(response) {
			response.device.ongattserverdisconnected = function(e) {
				if(typeof cleanup === "function") {
					cleanup(e)
				}
			}
			device.gatt.getPrimaryServices().then(function(services) {
				services.forEach(function(service) {
					service.getCharacteristics().then(function(characteristics) {
						characteristics.forEach(function(characteristic) {
							let id = {
								c: characteristic.uuid,
								s: service.uuid,
							}
							if(id.s in map && id.c in map[id.s]) {
								map[id.s][id.c](characteristic)
							}
						})
					}).catch(console.log)
				})
			}).catch(console.log)
		}).catch(console.log)
	}).catch(console.log)
}