JavaScript typeof

# JavaScript typeof, null, and undefined

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JavaScript typeof, null, undefined, valueOf().

## The typeof Operator

You can use the JavaScript typeof operator to find the type of a JavaScript variable.

## Example

typeof "John" // Returns string
typeof 3.14 // Returns number
typeof false // Returns boolean
typeof [1,2,3,4] // Returns object
typeof {name:'John', age:34} // Returns object
Try it yourself »

| In JavaScript, an array is a special type of object. Therefore typeof [1,2,3,4] returns object.

## Null

In JavaScript null is "nothing". It is supposed to be something that doesn't exist.

Unfortunately, in JavaScript, the data type of null is an object.

| You can consider it a bug in JavaScript that typeof null is an object. It should be null.

You can empty an object by setting it to null:

## Example

var person = null; // Value is null, but type is still an object
Try it Yourself »

You can also empty an object by setting it to undefined:

## Example

var person = undefined; // Value is undefined, type is undefined
Try it Yourself »

## Undefined

In JavaScript, undefined is a variable with no value.

The typeof a variable with no value is also undefined.

## Example

var person; // Value is undefined, type is undefined
Try it Yourself »

Any variable can be emptied, by setting the value to undefined. The type will also be undefined.

## Example

person = undefined; // Value is undefined, type is undefined
Try it Yourself »

## Difference Between Undefined and Null

typeof undefined // undefined
typeof null // object
null === undefined // false
null == undefined // true
Try it Yourself »
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