What is the Object.isPrototypeOf() method in Javascript?
The isPrototypeOf() method of the Object class in Javascript checks if an object is another object’s prototype. To determine the class of an object, the isPrototypeOf() method checks the entire prototype chain of the other object.
The process is illustrated below:
To use the isPrototypeOf() method, you will need to use the following command:
firstObj.isPrototypeOf(secondObj);
In the code shown above, firstObj and secondObj represent an instance of the Object class.
Parameters
The isPrototypeOf() method takes a single mandatory parameter, i.e., the object whose prototype chain must be checked.
Return value
The isPrototypeOf() method returns true if firstObj is the prototype of secondObj; otherwise, it returns false.
Example
The code below shows how the isPrototypeOf() method works in Javascript:
// initializing objectsvar objOne = new Object();function func(){};var array = [5, 10, 20];// checking valid prototype chainsconsole.log(Object.prototype.isPrototypeOf(objOne));console.log(Function.prototype.isPrototypeOf(func));console.log(Array.prototype.isPrototypeOf(array));//checking invalid prototype chainsconsole.log(Function.prototype.isPrototypeOf(array));console.log(Array.prototype.isPrototypeOf(objOne));
Explanation
First, the code initializes an empty object, function, and array. The isPrototypeOf() method is then used to evaluate the prototype chains of different combinations of classes and variables.
The first calls to the isPrototypeOf() method all return true because the objects objOne, func, and array are prototypes of the Object, Function, and Array classes, respectively.
On the other hand, the isPrototypeOf() method in line returns false because array belongs to the Array class but not the Function class. Similarly, the isPrototypeOf() method in line also returns false, as objOne is not a Function prototype, but rather an Object.
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