What I really wanted to know was would happen if I tried to unpack a value from an object that did not exist. And then what would subsequently happen if I tried to use that value in a spread operation. For example:
const testObj = {
a: [1, 2, 3],
b: [4, 5, 6]
}
const { a } = testObj;
const { b } = testObj;
const { c } = testObj;
const combined = [...a, ...b, ...c];
The short answer is this: if you try to destructure a non-existent property, then you get an undefined value. And if you try to use that undefined value in a spread operation, JavaScript will throw an error:
TypeError: undefined is not iterable (cannot read property Symbol(Symbol.iterator))
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