键/值对的值也可以是键吗？

Question

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In this example, to log the value of the properties with the keys "title" and "director", obj[key] is used. Since we're already in the execution context of the object: movie, in this example. Obj in "Obj[key]" must refer to title: 'a', and director: 'b' and key to the value of these objects, so "a" and "b" are noted as keys, right?

Can these "key-type" values also be logged with obj[value]?

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This is an example in a course, but the instructor is not explaining it well, so I've probably spent two hours at this point trying to understand the nomenclature. I hope this is correct, and if not; I'd really appreciate whatever misstep I'm making.

Thanks in advance

Answer 1

Putting the code from the image here for easier reference, have also changed the logs slightly to make it clear which is the key and which is the value:

 const movie = { title: 'a', releaseYar: 2018, rating: 4.5, director: 'b' }; showProperties(movie); function showProperties(obj) { for (let key in obj) if (typeof obj[key] === 'string') { console.log('key -->', key); console.log('value -->', obj[key]); } }

Nope, 'a' and 'b' in that example are not keys, they are values. In that example, movie is the object. The keys of the movie object are title , releaseYear , rating and director . Key is just another name for 'property' by the way.

In the showProperties function, you loop through each key -- ie. at every iteration, key is at first title , then releaseYear , and so on. obj[key] in the first iteration would be movie['title'] , which would give a value of a .

The console logs show the key, followed by the value of movie[key] . Hence the key of title , and the value of a for the first one.

Answer 2

Please look at the comment to understand the code and run code.

 const movie = { title: "SOmething", releaseDate: 2020, rating: 4.5, director: "Someone", }; function showProperties(object) { for (const key in object) { const value = object[key]; // get value of the key console.log(key, value); // log everything // check if value is type string if (typeof value === "string") { console.log(key, value); // then only if value is string } } } showProperties(movie);