What is the Return Value of typeof typeof 1?

Do you know, what is the return value of the following JavaScript expression?

typeof typeof 1

If you've guessed it was "string", then you were right. Let's take it apart to see why is that. The code above can be rewritten as:

typeof (typeof 1)

This can be broken down, further into two pieces:

• typeof 1
• typeof (<the return value of typeof 1>)

// This will return "number"
typeof 1

The first part will return "number", and it's type is a string:

// This will return "string"
typeof "number"

This means, that typeof typeof 1 will return "string".

50 JavaScript Interview Questions

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Resources:

• The typeof operator in JavaScript