Welcome to the Treehouse Community

The Treehouse Community is a meeting place for developers, designers, and programmers of all backgrounds and skill levels to get support. Collaborate here on code errors or bugs that you need feedback on, or asking for an extra set of eyes on your latest project. Join thousands of Treehouse students and alumni in the community today. (Note: Only Treehouse students can comment or ask questions, but non-students are welcome to browse our conversations.)

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and a supportive community. Start your free trial today.

JavaScript React Basics Introducing Props Iterating and Rendering with map()

Should I use constructor in react component or not?

I found that the tutorial simply define state inside the react component:

state = {
  score: 0

But I saw other online examples use constructor:

constructor(props) {
  this.state = {
    score: 0

I'm quite confused. Why they use constructor? For what cases I should use it?

1 Answer

Remi Vledder
Remi Vledder
14,144 Points

They are roughly the same: https://stackoverflow.com/questions/45451141/what-is-the-difference-between-using-constructor-vs-state-to-declare-state

The first example you show is using a method called "class field declaration". The second is the "constructor method", as described in the official React docs.

Generally it's a matter of preference. The class field declaration I personally find a bit easier to read.