在React中测试状态对象

Question

I've seen this question and it's helped with my understanding of how to set state correctly, but I'm struggling with the correct format of testing state based on a variable.

For example, I have this setState function call with a newItem variable:

addToSandwich(newItem){

    setState(prevState => {
        return { sandwichItems: {...prevState.sandwichItems, [newItem]: true} };
    });

}

And assuming the current state looks like this:

sandwichItems: {
    meat: true,
    cheese: true,
    tomato: false
}

With var newItem = "tomato";

It would result in this:

sandwichItems: {
    meat: true,
    cheese: true,
    tomato: true
}

---

But I am unable to test for newItem with:

var newItem = "tomato";

if (this.state.sandwichItems.newItem === true) {//whatever}

I would have to do:

if (this.state.sandwichItems.tomato === true) {//whatever}

---

How do I test for a value in state based on a variable's value?

Answer 1

This is what you want:

var newItem = "tomato";
if(this.state.sandwichItems[newItem] === true { }