JavaScript Interview Question #48: Dog-sized Cat

How many errors are in this code snippet? What’s the output?

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In JavaScript there are two ways to get access to the object properties.

• using the dot

  const dog = { name: 'Rex', age: 2, size: 'big' };

  console.log(dog.name); // Rex
  console.log(dog.age);  // 2
  console.log(dog.size); // big

• using square brackets

  const cat = { name: 'Tom', age: 5, big: false };

  console.log(cat['name']); // Tom
  console.log(cat['age']);  // 5
  console.log(cat['big']);  // false

Notice, that we’ve used field names as plain strings inside of the square brackets.

If we go to the original question, then the statement

console.log(cat[dog.size]);

Is the same as

console.log(cat['big']);

Which is equivalent to

console.log(cat.big);

In all three cases, we get access to the field big of the object cat.

ANSWER: There are no errors in the code snippet. The value false appears in the console when the code is executed.

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