JavaScript - typeof operator
The JavaScript typeof operator returns the type of a JavaScript variable or expression. The syntax for using this operator is given below:
Syntax
typeof operand typeof(operand)
Parameters
operand |
Specify an expression or a variable whose type is to be returned. |
Example:
In the example below, the typeof operator is used to find the datatype of a given variable or expression.
var txt;
//Numbers
txt = "typeof 25 : " + typeof 25 + "<br>";
txt = txt + "typeof 25.5 : " + typeof 25.5 + "<br>";
txt = txt + "typeof(10.5) : " + typeof(10.5) + "<br>";
txt = txt + "typeof(10 + 20) : " + typeof(10 + 20) + "<br><br>";
//Strings
txt = txt + "typeof '' : " + typeof '' + "<br>";
txt = txt + "typeof 'John' : " + typeof 'John' + "<br>";
txt = txt + "typeof 'John D' : " + typeof 'John D' + "<br><br>";
//Booleans
txt = txt + "typeof true : " + typeof true + "<br>";
txt = txt + "typeof false : " + typeof false + "<br>";
txt = txt + "typeof Boolean(1) : " + typeof Boolean(1) + "<br><br>";
//Symbols
txt = txt + "typeof Symbol() : " + typeof Symbol() + "<br>";
txt = txt + "typeof Symbol('foo') : " + typeof Symbol('foo') + "<br><br>";
//Undefined
txt = txt + "typeof undefined : " + typeof undefined + "<br><br>";
//Objects
txt = txt + "typeof {a: 1} : " + typeof {a: 1} + "<br>";
txt = txt + "typeof [1, 2, 3] : " + typeof [1, 2, 3] + "<br><br>";
//Functions
txt = txt + "typeof function() {} : " + typeof function() {} + "<br><br>";
The output (value of txt) after running above script will be:
typeof 25 : number
typeof 25.5 : number
typeof(10.5) : number
typeof(10 + 20) : number
typeof '' : string
typeof 'John' : string
typeof 'John D' : string
typeof true : boolean
typeof false : boolean
typeof Boolean(1) : boolean
typeof Symbol() : symbol
typeof Symbol('foo') : symbol
typeof undefined : undefined
typeof {a: 1} : object
typeof [1, 2, 3] : object
typeof function() {} : function
The following table summarizes the possible return values of typeof operator.
| Type | Result |
|---|---|
| Undefined | "undefined" |
| Null | "object" |
| Boolean | "boolean" |
| Number | "number" |
| BigInt | "bigint" |
| String | "string" |
| Symbol | "symbol" |
| Function object | "function" |
| Any other object | "object" |
❮ JavaScript - Operators
