What is constructor in javascript

It is a keyword. You cannot change the value of this. You cannot add a new property to an object constructor the same way you add a new property to an existing object:.

You cannot add a new method to an object constructor the same way you add a new method to an existing object. JavaScript knows which person you are talking about by "substituting" this with myMother. The Math object is not in the list. Math is a global object. The new keyword cannot be used on Math. As you can see above, JavaScript has object versions of the primitive data types String , Number , and Boolean.

But there is no reason to create complex objects. JavaScript Constructor Function In this tutorial, you will learn about JavaScript constructor function with the help of examples. In JavaScript, a constructor function is used to create objects. To create an object from a constructor function, we use the new keyword. JavaScript this Keyword In JavaScript, when this keyword is used in a constructor function, this refers to the object when the object is created.

JavaScript Constructor Function Parameters You can also create a constructor function with parameters. As shown above, console.

The constructor function is useful if you want to create multiple objects. You can have the same properties as the constructor function or add a new property to one particular object. Previous Tutorial:. Next Tutorial:. Share on:. Did you find this article helpful?

JavaTpoint offers too many high quality services. Mail us on [email protected] , to get more information about given services. Please mail your requirement at [email protected] Duration: 1 week to 2 week. JavaScript Tutorial. JS form validation JS email validation. JavaScript JavaScript Vs. Angular Js JavaScript vs. Next Topic JS static Method. Reinforcement Learning. R Programming. React Native. Having more than one occurrence of a constructor method in a class will throw a SyntaxError error.

This code snippet is taken from the classes sample live demo. Here the prototype of Square class is changed—but the constructor of its base class Polygon is still called when a new instance of a square is created. Leaving this out will cause a ReferenceError.