Updated swipe script for React

swipeFunc.js

import React, { Component } from 'react';
import update from 'react-addons-update';

export default class App extends Component {

	state = {
		touches: {
			touchstart: {
				x: -1,
				y: -1
			},
			touchmove: {
				x: -1,
				y: -1
			},
			distance: {
				x: -1,
				y: -1
			},
			touchend: false,
			direction: null
		}
	}

	componentDidMount() {
		window.addEventListener('touchstart', this.touchHandler, false);
		window.addEventListener('touchmove', this.touchHandler, false);
		window.addEventListener('touchend', this.touchHandler, false);
	}

	componentDidUnmount() {
		window.removeEventListener('touchstart', this.touchHandler, false);
		window.removeEventListener('touchmove', this.touchHandler, false);
		window.removeEventListener('touchend', this.touchHandler, false);
	}

	/**
	 * Difference
	 * Utility function to calculate the number of points between two numbers.
	 * @param  {number} num1
	 * @param  {number} num2
	 * @return {number}
	 */
	_difference = (num1, num2) => {
		return (num1 > num2) ? num1 - num2 : num2 - num1;
	}

	touchHandler = (event) => {
		let touch;
		if (typeof event !== 'undefined') {
			if (typeof event.touches !== 'undefined') {
				touch = event.touches[0];
				switch (event.type) {
					case 'touchstart':
					case 'touchmove': {
						const newState = update(this.state, {
							touches: {
								[event.type]: {
									x: { $set: touch.pageX },
									y: { $set: touch.pageY }
								},
								touchend: { $set: false }
							}
						});
						this.setState(newState);
						break;
					}
					case 'touchend': {
						if (
							this.state.touches.touchstart.y > -1 &&
							this.state.touches.touchmove.y > -1
						) {
							const newState = update(this.state, {
								touches: {
									direction: { $set: this.state.touches.touchstart.y < this.state.touches.touchmove.y ? 'down' : 'up' },
									distance: {
										x: { $set: this._difference(this.state.touches.touchstart.x, this.state.touches.touchmove.x) },
										y: { $set: this._difference(this.state.touches.touchstart.y, this.state.touches.touchmove.y) }
									},
									[event.type]: { $set: true }
								}
							});
							this.setState(newState);
						}
						break;
					}
					default:
						break;
				}
			}
		}
	}