The main difference between JavaScript instanceof and typeof operator is check whether the prototype property or type of primitive values.
The instanceof operator tests whether the prototype property of a constructor appears anywhere in the prototype chain of an object.
class Foo {};
let foo = new Foo();
console.log(foo instanceof Foo);The typeof The operator is used for getting the type of primitive values mainly. The typeof operator tests whether the value belongs to one of six basic types: “number“, “string“, “boolean“, “object“, “function” or “undefined“.
console.log(typeof 1);Example instanceof vs typeof in JavaScript
Simple example code.
<!DOCTYPE html>
<html>
<body>
<script>
function Bar (){};
let bar = new Bar();
console.log("instance of", bar instanceof Bar);
let n = 1;
let s = '1';
console.log("typeof" ,typeof (n + s));
</script>
</body>
</html> Output:
Use instanceof for custom types:
var ClassFirst = function () {};
var ClassSecond = function () {};
var instance = new ClassFirst();
typeof instance; // object
typeof instance == 'ClassFirst'; // false
instance instanceof Object; // true
instance instanceof ClassFirst; // true
instance instanceof ClassSecond; // false
Use typeof for simple built-in types:
'example string' instanceof String; // false
typeof 'example string' == 'string'; // true
'example string' instanceof Object; // false
typeof 'example string' == 'object'; // false
true instanceof Boolean; // false
typeof true == 'boolean'; // true
99.99 instanceof Number; // false
typeof 99.99 == 'number'; // true
function() {} instanceof Function; // true
typeof function() {} == 'function'; // true
Use instanceof for complex built-in types:
/regularexpression/ instanceof RegExp; // true
typeof /regularexpression/; // object
[] instanceof Array; // true
typeof []; //object
{} instanceof Object; // true
typeof {}; // object
And the last one is a little bit tricky:
typeof null; // objectComment if you have any doubts or suggestions on this JS difference topic.
Note: The All JS Examples codes are tested on the Firefox browser and the Chrome browser.
OS: Windows 10
Code: HTML 5 Version