SimpleTween.js

class SimpleTween extends Component {
	static defaultProps = { duration: 1000 }

	constructor(props) {
		super(props);

		this.state = {
			timeStart: +new Date(),
			current: props.start,
		};
		this.calculate = this._calculate.bind(this);
	}
	
	componentDidMount() {
		this.timer = setInterval(this.calculate, 1000 / 60);
	}

	componentWillUnmount() {
		if (this.timer) {
			clearInterval(this.timer);
		}
	}

	_calculate() {
		const { duration, start, end } = this.props;
		const { timeStart } = this.state;

		const time = +new Date() - timeStart;

		if (time > duration) {
			this.setState(() => ({
				current: end,
			}));
			return;
		}

		const currentPosition = linear(time, start, end - start, duration);
		
		this.setState(() => ({
			current: currentPosition,
		}));
	}

	render() {
		const { children } = this.props;
		const { current } = this.state;

		return children({ current });
	}
}