Tutorial: Working with Datetime Type in TypeScript

Date Type in TypeScript

In TypeScript, the Date type represents a specific point in time, including the date and time. It is a built-in type in JavaScript and can be used directly in TypeScript. Here is an example of using the Date type in TypeScript:

const currentDate: Date = new Date();
console.log(currentDate); // Output: Sun Oct 31 2021 15:18:23 GMT+0530 (India Standard Time)

We can also create a Date object by specifying the year, month, day, hour, minute, second, and millisecond values. The month value starts from 0 for January, so we need to subtract 1 from the desired month value. Here is an example:

const specificDate: Date = new Date(2021, 9, 31, 15, 30, 0, 0);
console.log(specificDate); // Output: Sun Oct 31 2021 15:30:00 GMT+0530 (India Standard Time)

Time Type in TypeScript

Unlike some other programming languages, TypeScript does not have a separate Time type. Instead, the Date type represents both the date and time. However, we can extract the time component from a Date object using various methods provided by the Date class.

For example, to get the current time in hours, minutes, and seconds, we can use the getHours(), getMinutes(), and getSeconds() methods respectively. Here is an example:

const currentTime: Date = new Date();
const hours: number = currentTime.getHours();
const minutes: number = currentTime.getMinutes();
const seconds: number = currentTime.getSeconds();
console.log(`Current time: ${hours}:${minutes}:${seconds}`);

Output:

Current time: 15:40:30

Datetime Format in TypeScript

The Date type in TypeScript provides several methods to format the date and time according to specific requirements. One commonly used method is toLocaleString(), which returns a string representing the date and time using the current locale of the user’s browser. Here is an example:

const currentDate: Date = new Date();
const formattedDate: string = currentDate.toLocaleString();
console.log(formattedDate); // Output: 10/31/2021, 3:48:15 PM

Another useful method is toISOString(), which returns a string representing the date and time in ISO 8601 format. Here is an example:

const currentDate: Date = new Date();
const isoString: string = currentDate.toISOString();
console.log(isoString); // Output: 2021-10-31T10:18:23.000Z

Datetime Validation in TypeScript

Validating datetime inputs is an important task in any application. TypeScript provides built-in methods to perform datetime validation. One such method is isNaN(), which can be used to check if a given date is valid or not. Here is an example:

const invalidDate: Date = new Date('2021-13-01');
console.log(isNaN(invalidDate.getTime())); // Output: true

const validDate: Date = new Date('2021-10-31');
console.log(isNaN(validDate.getTime())); // Output: false

In the above example, the getTime() method is used to get the numeric value representing the date. If the value is NaN, it means the date is invalid.

Datetime Conversion in TypeScript

In TypeScript, we can convert a Date object to different formats using various methods provided by the Date class. One common conversion is to convert a Date object to a timestamp, which represents the number of milliseconds since January 1, 1970. We can use the getTime() method to achieve this. Here is an example:

const currentDate: Date = new Date();
const timestamp: number = currentDate.getTime();
console.log(timestamp); // Output: 1635677895000

To convert a timestamp back to a Date object, we can use the Date constructor and pass the timestamp as an argument. Here is an example:

const timestamp: number = 1635677895000;
const convertedDate: Date = new Date(timestamp);
console.log(convertedDate); // Output: Sun Oct 31 2021 15:48:15 GMT+0530 (India Standard Time)

Datetime Manipulation in TypeScript

Manipulating datetime values is a common requirement in many applications. TypeScript provides several methods to manipulate Date objects. One such method is setFullYear(), which allows us to set the year of a Date object. Here is an example:

const currentDate: Date = new Date();
currentDate.setFullYear(2022);
console.log(currentDate); // Output: Wed Oct 31 2022 15:48:15 GMT+0530 (India Standard Time)

Similarly, we can use methods like setMonth(), setDate(), setHours(), setMinutes(), setSeconds(), and setMilliseconds() to manipulate other components of a Date object.

Datetime Library in TypeScript

While TypeScript provides built-in support for working with Date objects, there are also several third-party libraries available that offer additional functionality and convenience. One popular library is moment.js, which provides a simple and flexible API for parsing, manipulating, and formatting dates. Here is an example of using moment.js in TypeScript:

First, install the moment.js library using npm:

npm install moment

Then, import the library in your TypeScript file:

import * as moment from 'moment';

const currentDate: moment.Moment = moment();
console.log(currentDate.format('YYYY-MM-DD')); // Output: 2021-10-31

In the above example, we create a moment object using the moment() function and then format it using the format() method.

Datetime Comparison in TypeScript

Comparing datetime values is often required in applications. TypeScript provides several methods to compare Date objects. One such method is getTime(), which returns the numeric value representing the date. We can use this value to compare two Date objects. Here is an example:

const date1: Date = new Date('2021-10-31');
const date2: Date = new Date('2022-01-01');

if (date1.getTime() < date2.getTime()) {
  console.log('date1 is before date2');
} else if (date1.getTime() > date2.getTime()) {
  console.log('date1 is after date2');
} else {
  console.log('date1 and date2 are equal');
}

In the example above, we use the getTime() method to get the numeric value representing each date and then compare them using the < and > operators.

Datetime Parsing in TypeScript

Parsing datetime strings is a common task when working with dates and times. TypeScript provides the Date constructor, which can parse a wide range of date and time formats. Here is an example:

const dateString: string = '2021-10-31T15:48:15.000Z';
const parsedDate: Date = new Date(dateString);
console.log(parsedDate); // Output: Sun Oct 31 2021 21:18:15 GMT+0530 (India Standard Time)

In the above example, we pass the datetime string to the Date constructor, which automatically parses it and creates a Date object.

Datetime Arithmetic in TypeScript

Performing arithmetic operations with datetime values is often required in applications. TypeScript provides several methods to perform arithmetic operations on Date objects. One such method is getTime(), which returns the numeric value representing the date. We can use this value to perform arithmetic operations. Here is an example:

const currentDate: Date = new Date();
const futureDate: Date = new Date(currentDate.getTime() + 24 * 60 * 60 * 1000); // Add one day (24 hours) to the current date
console.log(futureDate); // Output: Mon Nov 01 2021 15:48:15 GMT+0530 (India Standard Time)

In the example above, we add one day (24 hours) to the current date by adding the number of milliseconds in one day to the current timestamp.

Related Article: Tutorial on Exact Type in TypeScript

Defining a Date Type in TypeScript

In TypeScript, we can define our own custom types to represent dates. This can be useful when we want to add additional properties or methods to the Date type. Here is an example:

type CustomDate = {
  date: Date;
  format: () => string;
};

const currentDate: CustomDate = {
  date: new Date(),
  format: function () {
    return this.date.toLocaleString();
  },
};

console.log(currentDate.format()); // Output: 10/31/2021, 3:48:15 PM

In the example above, we define a CustomDate type with properties date of type Date and format of type function. We then create an object of type CustomDate and use the format method to format the date.

Syntax for Specifying a Time Type in TypeScript

As mentioned earlier, TypeScript does not have a separate Time type. The Date type represents both the date and time. If you want to specify a specific time without the date component, you can create a Date object with a specific date and then set the year, month, and day to a fixed value, such as 1970-01-01. Here is an example:

const specificTime: Date = new Date(1970, 0, 1, 15, 30, 0, 0);
console.log(specificTime); // Output: Thu Jan 01 1970 15:30:00 GMT+0530 (India Standard Time)

In the example above, we set the year, month, and day to 1970-01-01 and then set the hour, minute, and second to the desired time.

Formatting a Datetime Value in TypeScript

Formatting a datetime value is often required when displaying dates and times in a specific format. TypeScript provides several methods to format Date objects. One common method is toLocaleString(), which returns a string representing the date and time using the current locale of the user’s browser. We can also use the toLocaleDateString() and toLocaleTimeString() methods to format only the date or time component respectively. Here is an example:

const currentDate: Date = new Date();
const formattedDateTime: string = currentDate.toLocaleString();
console.log(formattedDateTime); // Output: 10/31/2021, 3:48:15 PM

const formattedDate: string = currentDate.toLocaleDateString();
console.log(formattedDate); // Output: 10/31/2021

const formattedTime: string = currentDate.toLocaleTimeString();
console.log(formattedTime); // Output: 3:48:15 PM

In the example above, we use the toLocaleString(), toLocaleDateString(), and toLocaleTimeString() methods to format the current date and time.

Validating a Datetime Input in TypeScript

Validating a datetime input is important to ensure that the user provides a valid date and time. TypeScript provides built-in methods to perform datetime validation. One such method is isNaN(), which can be used to check if a given date is valid or not. We can also use regular expressions to validate datetime inputs. Here is an example:

function validateDatetimeInput(datetime: string): boolean {
  const regex: RegExp = /^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}.\d{3}Z$/;
  return regex.test(datetime);
}

const datetime1: string = '2021-10-31T15:48:15.000Z';
console.log(validateDatetimeInput(datetime1)); // Output: true

const datetime2: string = '2021-13-01T15:48:15.000Z';
console.log(validateDatetimeInput(datetime2)); // Output: false

In the example above, we define a validateDatetimeInput function that uses a regular expression to validate datetime inputs.

Manipulating Datetime Values in TypeScript

Manipulating datetime values is often required in applications. TypeScript provides several methods to manipulate Date objects. One such method is setFullYear(), which allows us to set the year of a Date object. We can also use methods like setMonth(), setDate(), setHours(), setMinutes(), setSeconds(), and setMilliseconds() to manipulate other components of a Date object. Here is an example:

const currentDate: Date = new Date();
currentDate.setFullYear(2022);
currentDate.setMonth(0);
currentDate.setDate(1);
currentDate.setHours(0);
currentDate.setMinutes(0);
currentDate.setSeconds(0);
currentDate.setMilliseconds(0);

console.log(currentDate); // Output: Sat Jan 01 2022 00:00:00 GMT+0530 (India Standard Time)

In the example above, we set the year, month, date, hours, minutes, seconds, and milliseconds components of the Date object to specific values.

Recommended Datetime Libraries for TypeScript

1. Luxon: Luxon provides an easy-to-use and useful API for working with dates and times. It offers features like parsing, formatting, manipulation, and localization. You can find more information and examples in the official documentation: Luxon Documentation.

2. date-fns: date-fns is a lightweight and modular library for working with dates. It provides a wide range of functions for parsing, formatting, manipulation, and localization. You can find more information and examples in the official documentation: date-fns Documentation.

3. Day.js: Day.js is a fast and minimalist library for parsing, formatting, and manipulating dates. It has a small footprint and is compatible with most modern browsers. You can find more information and examples in the official documentation: Day.js Documentation.

These libraries offer various features and capabilities, so choose the one that best suits your needs and project requirements.

Comparing Two Datetime Values in TypeScript

const date1: Date = new Date('2021-10-31');
const date2: Date = new Date('2022-01-01');

if (date1.getTime() < date2.getTime()) {
  console.log('date1 is before date2');
} else if (date1.getTime() > date2.getTime()) {
  console.log('date1 is after date2');
} else {
  console.log('date1 and date2 are equal');
}

In the example above, we use the getTime() method to get the numeric value representing each date and then compare them using the < and > operators.

Parsing a Datetime String in TypeScript

Parsing datetime strings is a common task when working with dates and times. TypeScript provides the Date constructor, which can parse a wide range of date and time formats. Here is an example:

const dateString: string = '2021-10-31T15:48:15.000Z';
const parsedDate: Date = new Date(dateString);
console.log(parsedDate); // Output: Sun Oct 31 2021 21:18:15 GMT+0530 (India Standard Time)

In the above example, we pass the datetime string to the Date constructor, which automatically parses it and creates a Date object.

Performing Arithmetic Operations with Datetime Values in TypeScript

const currentDate: Date = new Date();
const futureDate: Date = new Date(currentDate.getTime() + 24 * 60 * 60 * 1000); // Add one day (24 hours) to the current date
console.log(futureDate); // Output: Mon Nov 01 2021 15:48:15 GMT+0530 (India Standard Time)

In the example above, we add one day (24 hours) to the current date by adding the number of milliseconds in one day to the current timestamp.

Related Article: Building a Rules Engine with TypeScript

TypeScript Decorators for Datetime Handling

TypeScript decorators are a useful feature that allows us to add metadata to classes, properties, and methods, enabling us to enhance their behavior or add additional functionality. While decorators are not specifically designed for datetime handling, we can create custom decorators to handle datetime-related tasks in TypeScript. Here is an example of a custom decorator for formatting datetime values:

function formatDatetime(target: any, propertyKey: string) {
  const originalValue = target[propertyKey];

  const getter = function () {
    const datetime: Date = originalValue.call(this);
    return datetime.toLocaleString();
  };

  Object.defineProperty(target, propertyKey, {
    get: getter,
  });
}

class Example {
  @formatDatetime
  getCurrentDatetime(): Date {
    return new Date();
  }
}

const example = new Example();
console.log(example.getCurrentDatetime()); // Output: 10/31/2021, 3:48:15 PM

In the example above, we define a formatDatetime decorator that wraps the getter function of the getCurrentDatetime method. Inside the decorator, we get the original datetime value, format it using the toLocaleString() method, and return the formatted value.

External Sources

– Luxon Documentation
– date-fns Documentation
– Day.js Documentation