Typescript add and subtract days, months, years to Date | extension examples

Typescript add and subtract days, months, years to Date | extension examples

This tutorial explains how to add a day, month, and year to the current date in Typescript with examples

Typescript date add days, months, year

Create a function that takes the date and number of days and adds the days to the date object and returns the Date object.

function addDays(date: Date, days: number): Date {
  date.setDate(date.getDate() + days);
  return date;
}
console.log(new Date());
console.log(addDays(new Date(), 2));

Output:

"2022-10-19T03:44:33.834Z"
"2022-10-21T03:44:33.839Z" `

To add 2 months, pass 60 days to the addDays function.

console.log(new Date());
console.log(addDays(new Date(),60));

Output:

"2022-10-19T03:45:41.756Z"
"2022-12-18T03:45:41.759Z"

Adding 1 year gives next year’s date, ie pass 366 days

console.log(new Date());
console.log(addDays(new Date(),366));

Output:

"2022-10-19T03:46:37.901Z"
"2023-10-20T03:46:37.906Z"

Typescript date extension to get Weekname

Suppose you want to get today’s weekname for a given date.

  • Create an Interface with an abstract method - getWeekName that returns a string name such as Sunday.
  • Add the prototype implementation for the getWeekName to the Date class
  • Inside a method, Constructed an array of week names.
  • Date.getDays returns the day of a current week
  • Finally, Return the weekname from a given day.
interface Date {
  getWeekName: () => String;
}

Date.prototype.getWeekName = function () {
  var date = new Date();
  var weekNames = new Array(7);
  weekNames[0] = "Sunday";
  weekNames[1] = "Monday";
  weekNames[2] = "Tuesday";
  weekNames[3] = "Wednesday";
  weekNames[4] = "Thursday";
  weekNames[5] = "Friday";
  weekNames[6] = "Saturday";
  return weekNames[date.getDay()];
};
console.log(new Date().getWeekName());

you can also add a days extension

Typescript extension adding days to Date class

interface Date {
  addDays: (days: number) => Date;
}

Date.prototype.addDays = function (days: number) {
  let valueDate = this.valueOf();
  valueDate += 86400000 * days;
  return new Date(valueDate);
};

console.log(new Date().addDays(1));

Typescript date extension subtracts days, months, years

This example subtracts days, months years from a given date

interface Date {
  addDays: (days: number) => Date;
  subtractDays: (days: number) => Date;
}

Date.prototype.addDays = function (days: number) {
  var valueDate = this.valueOf();
  valueDate += 86400000 * days;
  return new Date(valueDate);
};
Date.prototype.subtractDays = function (days: number) {
  var valueDate = this.valueOf();
  valueDate -= 86400000 * days;
  return new Date(valueDate);
};
console.log(new Date().substractDays(1));

Output:

"2023-10-20T03:58:35.944Z";
"2022-10-30T03:58:35.947Z";

Typescript Subtract add days, months, year

Create a function subtractDays that takes the date and number of days and subtracts the days to date object and returns the Date object.

Here is an example to subtract 2 days from a given current date.

function subtractDays(date: Date, days: number): Date {
  var valueDate = date.valueOf();
  valueDate -= 86400000 * days;
  return new Date(valueDate);
}
console.log(new Date());
console.log(substractDays(new Date(), 2));

Output:

"2022-10-19T03:44:33.834Z"
"2022-10-21T03:44:33.839Z" `

To subtract 2 months from a current date, pass 60 days to the addDays function.

console.log(new Date());
console.log(subtractDays(new Date(), 60));

Output:

"2022-10-19T03:45:41.756Z"
"2022-08-18T03:45:41.759Z"

Subtract 1 year gives the previous year’s date, ie pass 366 days to the function

console.log(new Date());
console.log(substractDays(new Date(), 366));

Output:

"2022-10-19T03:46:37.901Z"
"20231-10-20T03:46:37.906Z"