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Coderslang: Become a Software Engineer
Coderslang: Become a Software Engineer

Posted on • Originally published at learn.coderslang.com

JS Test #7: Is this an array?

Is array an array?

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At line one we create an array and bind it with the array constant. Then the type of the value of this constant is evaluated by the typeof operator.

There’s no such type as array in JS, so it’s impossible to see the message ARRAY! on the screen. In fact, all JS arrays are objects, so the execution goes into the else branch, and SOMETHING WEIRD is printed on the screen.


ANSWER: SOMETHING WEIRD will be logged to the screen as all JS arrays have the type object.

Discussion (3)

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lionelrowe profile image
lionel-rowe

Array.isArray(array) or array instanceof Array would both work 😉

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coderslang profile image
Coderslang: Become a Software Engineer Author

Thanks for pointing it out! The main point of these code snippets is to show beginner devs their weaknesses. In my experience, at least half of the newbie devs don't know how exactly typeof works.

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shashankgopannagari profile image
Shashank

Object.prototype.toString.call([]).slice(8,-1);
will also work