Why parentheses here but not here

JavaScript
1

Why no parentheses here:

toggleVisibility() {
    this.setState(state => {
      if (state.visibility === true) {
         return { visibility: false };
       } else {
         return { visibility: true };
      }
    });

But here there are:

 increment() {
    this.setState(state => ({
      count: state.count + 1
    }));

Thanks,

Andrej

2

Accoding to MDN

It looks like you “Parenthesize the body of a function to return an object literal expression”.

1 Like
3

the first one, you have explicit return, so the graph parenthesis are of the function body

the second one you have implicit return and the {} are of an object, if you don’t put the round parenthesis around the object, the graph parenthesis are considered those of the function body, and as such name: "value" is wrong sintax loose inside a function

5

Why does this code not work:

reset() {
      this.setState(state => ({count: 0}))
    }

And this code does:

reset() {
    this.setState({
      count: 0
    });

I fixed it like this:

reset() {
      this.setState(state => ({count: state.count - state.count}))
    }

But is this the only way?

6

here you do not have a function…

state.count - state.count makes 0, you can just have count: 0 inside that object instead of count: state.count - state.count