Below is the example of the typeof operator.
- Example:
<script>
// "string"
document.write(
typeof
'mukul'
+
"<br>"
)
// "number"
document.write(
typeof
25 +
"<br>"
)
// "undefined"
document.write(
typeof
variable)
</script>
chevron_rightfilter_none - Output:
string number undefined
In JavaScript, the typeof operator returns the data type of its operand in the form of a string. The operand can be any object, function, or variable.
Syntax:
typeof operand
OR
typeof (operand)
Note: Operand is an expression representing the object or primitive whose type is to be returned.
The possible types that exists in javascript are:
- undefined
- Object
- boolean
- number
- string
- symbol
- function
Example:
<script> // "string" document.write( typeof 'mukul' + "<br>" ) // "number" document.write( typeof 25 + "<br>" ) // "undefined" document.write( typeof variable) </script> |
Output:
string number undefined
Let’s cover all the types one by one dedicating a single code section for each code.
Example: Typeof Number, in this sample, we used ‘===’ (strict equality comparison operator) which compare value and type both and then return true or false. For example- consider the first console.log(), the js starts compiling from left to right and it first calculates the type of 25 which is ‘number’ and then compares it with ‘number’ and then finally returns true or false accordingly.
<script> //Number console.log( typeof 25 === 'number' ); console.log( typeof 3.14 === 'number' ); console.log( typeof (69) === 'number' ); // log base 10 console.log( typeof Math.LN10 === 'number' ); console.log( typeof Infinity === 'number' ); // Despite being "Not-A-Number" console.log( typeof NaN === 'number' ); // Wrapping in Number() function console.log( typeof Number( '100' ) === 'number' ); </script> |
Output:
Fun fact NaN which stands for not-a-number has a type of “number”.
Example: Typeof string
<script> // string console.log( typeof '' === 'string' ); console.log( typeof 'bla' === 'string' ); // ES6 template literal console.log( typeof `template literal` === 'string' ); console.log( typeof '1' === 'string' ); console.log( typeof ( typeof 1) === 'string' ); // Wrapping inside String() function console.log( typeof String(1) === 'string' ); </script> |
Output:
Examople: Typeof boolean
<script> // Boolean console.log( typeof true === 'boolean' ); console.log( typeof false === 'boolean' ); // Two calls of the ! (logical NOT) operator // are equivalent to Boolean() console.log( typeof !!(1) === 'boolean' ); </script> |
Output:
Example: Typeof undefined
<script> // Undefined console.log( typeof undefined === 'undefined' ); // Declared but undefined variable console.log( typeof variable === 'undefined' ); </script> |
Output:
Example: Typeof symbol
<script> // Symbol console.log( typeof Symbol() === 'symbol' ); console.log( typeof Symbol( 'party' ) === 'symbol' ); console.log( typeof Symbol.iterator === 'symbol' ); </script> |
Output:
Example: Typeof object
<script> // Object console.log( typeof {b: 1} === 'object' ); console.log( typeof [1, 2, 9] === 'object' ); console.log( typeof new Date() === 'object' ); </script> |
Output:
Example: Typeof function
<script> // function console.log( typeof function () {} === 'function' ); //classes too are objects console.log( typeof class C {} === 'function' ); console.log( typeof Math.sin === 'function' ); sin function (maths) </script> |
Output: