javascript - typeof Number equals Number - Stack Overflow

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In JavaScript,

1. typeof 42 === 'number' //true

evaluates to true. But..

2. typeof Number === 'number' //false

evalutes to false. And..

3. typeof 'number' === 'number' //false

also evaluates to false.

Shouldn't parison 2 or 3 evaluate to true?

In JavaScript,

1. typeof 42 === 'number' //true

evaluates to true. But..

2. typeof Number === 'number' //false

evalutes to false. And..

3. typeof 'number' === 'number' //false

also evaluates to false.

Shouldn't parison 2 or 3 evaluate to true?

• javascript
• numbers
• typeof

Share Improve this question Follow edited Jan 13, 2015 at 20:15 JLRishe 102k1919 gold badges137137 silver badges171171 bronze badges asked Jan 13, 2015 at 19:28 FungyBytesFungyBytes 41311 gold badge66 silver badges1414 bronze badges 3

• 1 Why do you expect typeof 'number' to return 'number'? What do you expect typeof 'foo' to return? – Felix Kling Commented Jan 13, 2015 at 19:40
• I see now. typeof 'foo' returns 'string'. I guess I was confused because the return value of typeof is quoted. – FungyBytes Commented Jan 13, 2015 at 19:45
• 1 typeof always returns a string. – Felix Kling Commented Jan 13, 2015 at 19:49

Add a ment  | 

2 Answers 2

Sorted by: Reset to default 4

No, Number, String, and Boolean are all objects (and functions). typeof applied to any of them will return the value "function".

https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/String https://developer.mozilla/en-US/docs/Web/JavaScript/Reference/Global_Objects/Boolean


The value 'number' is a string and therefore its type is 'string'.

Number is a function which you can use to wrap a native value into a Numberobject. Number is the also the constructor of the Number type, if used with new, e.g.

new Number(42)

From the documentation:

A Number object is created using the Number() constructor.

So typeof Number is actually "function".

On the other hand, 'number' is a String, so typeof 'number' is "string"

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