Why is setState in reactjs Async instead of Sync?

Question

I have just found that in react this.setState() function in any component is asynchronous or is called after the completion of the function that it was called i

Answer 1

You can call a function after the state value has updated:

this.setState({foo: 'bar'}, () => { 
    // Do something here. 
});

Also, if you have lots of states to update at once, group them all within the same setState:

Instead of:

this.setState({foo: "one"}, () => {
    this.setState({bar: "two"});
});

Just do this:

this.setState({
    foo: "one",
    bar: "two"
});