JavaScript OOP's Part 4 : instanceOf , indexOf and hasOwnProperty

JavaScript OOP's Part 4 : instanceOf , indexOf and hasOwnProperty

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SURYA L
·Jul 24, 2022·

3 min read

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Table of contents

  • What is indexOf( )?
  • What is hasOwnProperty( ) in JavaScript ?
  • What is instanceOf ?
  • Conclusion:

Hello everyone hope you are all doing well, My name is Surya L.

In this blog we will Learn instanceOf , indexOf and hasOwnProperty in JavaScript.

What is indexOf( )?

indexOf is an JavaScript Operation which is used to returns the first index at which a given element can be found in the array, or -1 if it is not present.

  • Syntax:
arrrayName.indexOf(elementName);

Example for indexOf

const names=["Apple","Bat","Cat","Dog","Elephant","Frog","Giraffe","Zebra"];
//indexof is used to find the index of the element in the array
console.log("Output :",names.indexOf("Elephant"));
//returns 4 as array starts from 0
  • Output would be 4

What is hasOwnProperty( ) in JavaScript ?

If an object owns a property (rather than inheriting), hasOwnProperty() returns a boolean. It returns true if the object has that property, false otherwise.

Example for hasOwnProperty( )

let people={
    John: {
        age: 20,
        job: 'teacher'
    },
    Jane: {
        age: 21,
        job: 'designer'
    },
    Joe: {
        age: 22,
        job: 'driver'
    }
    ,
    Karen: {
        age: 23,
        job: 'doctor'
    }
}
console.log(people.hasOwnProperty('John'));
//Would return as true as John is a property of people object
console.log(people.hasOwnProperty('James'));
//Would return as false as James is a property of people object

Output:

  • people.hasOwnProperty('John')) Would return as true as John is a property of people object.

  • people.hasOwnProperty('James')) Would return as false as James is not a property of people object.

What is instanceOf ?

instanceOf checks whether a constructor's prototype property is present anywhere in an object's prototype chain. A Boolean value is returned.

Example

let Bird = function(name, color) {
  this.name = name;
  this.color = color;
  this.numLegs = 2;
}

let crow = new Bird("Alexis", "black");

crow instanceof Bird;//This instanceof method would return true.

instanceOf will verify that an object is not an instance of the constructor if it is created without using it:

let canary = {
  name: "Mildred",
  color: "Yellow",
  numLegs: 2
};

canary instanceof Bird;
//This instanceof method would return false.

Conclusion:

  • indexOf is an JavaScript Operation which is used to returns the first index at which a given element can be found in the array, or -1 if it is not present.

  • If an object owns a property (rather than inheriting), hasOwnProperty() returns a boolean. It returns true if the object has that property, false otherwise.

  • instanceOf checks whether a constructor's prototype property is present anywhere in an object's prototype chain. A Boolean value is returned.

Thanks for reading the blog. Do let me know what you think about it.

Reference: I learned this topic from freecodecamp and MDN which I have minified. You can find me at Showwcase, Linkedin , Twitter , GitHub , Email .

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