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JavaScript React Basics (2018) Understanding State Understanding State Review

Posted by Garrett Hughes
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Garrett Hughes
Python Development Techdegree Student 32,971 Points

I can't figure out what's suppose to go here. I've reviewed the videos a few times. I guess I'm just missing it.

Complete the code so that the isConfirmed state updates its value based on the previous state.

confirmGuest = () => {
  this.setState( prevState => ({ 
    isConfirmed: !___.isConfirmed
  }));
}

2 Answers

Garrett Hughes
.a{fill-rule:evenodd;}techdegree
Garrett Hughes
Python Development Techdegree Student 32,971 Points

Oh, because it's just changing a boolean value to its opposite. I was thinking it wasnted a '!== prevState.isConfirmed" or something like that and it wasn't clicking lol Dumb question.

Garrett Hughes
seal-mask
.a{fill-rule:evenodd;}techdegree
Garrett Hughes
Python Development Techdegree Student 32,971 Points
Garrett Hughes
.a{fill-rule:evenodd;}techdegree
Garrett Hughes
Python Development Techdegree Student 32,971 Points

Ooo. It's just "prevState". But why is there an '!' before it? That's what was throwing me off.

Gabbie Metheny
Gabbie Metheny
33,778 Points

! is the logical NOT operator. In this case, it's basically just a quick way of flipping the boolean value. If the isConfirmed state was true, firing this event handler would change it to false; and if it started as false, the handler would flip it to true. Similar to using if/else if logic, but without explicitly writing it all out, since you just want the boolean to flip to the only other option.