Javascript - Date prototype Property

The prototype constructor allows you to add new properties and methods to the Date() class.

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Description

The prototype constructor allows you to add new properties and methods to the Date() class.

Syntax 

Date.prototype.name = value

Example

The following code creates a new date method that gives the date object a month-name property called myProp:

Demo

//call the new myMet() method, and display this month's name, using the new myProp property.
Date.prototype.myMet = function() {
    if (this.getMonth() == 0){this.myProp = "January"};
    if (this.getMonth() == 1){this.myProp = "February"};
    if (this.getMonth() == 2){this.myProp = "March"};
    if (this.getMonth() == 3){this.myProp = "April"};
    if (this.getMonth() == 4){this.myProp = "May"};
    if (this.getMonth() == 5){this.myProp = "June"};
    if (this.getMonth() == 6){this.myProp = "July"};
    if (this.getMonth() == 7){this.myProp = "August"};
    if (this.getMonth() == 8){this.myProp = "September"};
    if (this.getMonth() == 9){this.myProp = "October"};
    if (this.getMonth() == 10){this.myProp = "November"};
    if (this.getMonth() == 11){this.myProp = "December"};
};


var d = new Date();
d.myMet();/*w  w  w  .j  a v a  2s . c  om*/
console.log(d.myProp);

Result