Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

JavaScript React Components (2018) Stateful Components and Lifecycle Methods Update the Stopwatch State with componentDidMount()

Ankit Upadhyay
Ankit Upadhyay
556 Points

Update the Stopwatch

Shouldn't the difference of now and this.state.previousTime always becomes zero because as tick() function getting called , we're updating previousTime with now.
So again subtracting , now with this.state.previousTime` shouldn't become zero ?

Here is the code :

tick = () => {
    if(this.state.isRunning) {
        const now = Date.now();
        this.setState( prevState => ({
            previousTime: now,
            elapsedTime: prevState.elapsedTime + (now - this.state.previousTime)