Lære Using Built-in Formatting Methods | Formatting and Comparing Dates

When displaying dates to users, you must often present them in a format that is clear, readable, and appropriate for your audience. JavaScript provides several built-in methods on the Date object that allow you to quickly and easily format dates for display without additional libraries. These methods include toDateString(), toLocaleString(), and toISOString(), each serving different formatting purposes and audiences.


              12
            
const today = new Date();
console.log(today.toDateString());


              1234567891011
            
const eventDate = new Date('2024-12-25T15:30:00Z');

// US English, with time
console.log(eventDate.toLocaleString('en-US')); // "12/25/2024, 10:30:00 AM"

// British English, with time
console.log(eventDate.toLocaleString('en-GB')); // "25/12/2024, 15:30:00"

// Custom options: only date, long format
console.log(eventDate.toLocaleString('en-US', { year: 'numeric', month: 'long', day: 'numeric' }));
// "December 25, 2024"

For cases where you need a standardized, machine-readable date format—such as for storing dates in databases, exchanging data between systems, or working with APIs—the toISOString() method is ideal. This method returns a string in the ISO 8601 extended format, which looks like "YYYY-MM-DDTHH:mm:ss.sssZ". The output is always in Coordinated Universal Time (UTC). For example, calling new Date().toISOString() might produce "2024-06-17T09:23:45.123Z", which can be reliably parsed by most programming languages and systems.

Each of these built-in formatting methods has its strengths and limitations:

toDateString() is quick and simple for basic, human-friendly date displays, but does not allow customization or localization;
toLocaleString() is highly flexible and supports localization and various formatting options, but its output can vary across browsers and environments;
toISOString() provides a universal, consistent format suitable for data interchange, but is not user-friendly for most audiences.

Understanding when to use each method will help you present dates clearly and appropriately in your applications.

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              12
            
const today = new Date();
console.log(today.toDateString());


              1234567891011
            
const eventDate = new Date('2024-12-25T15:30:00Z');

// US English, with time
console.log(eventDate.toLocaleString('en-US')); // "12/25/2024, 10:30:00 AM"

// British English, with time
console.log(eventDate.toLocaleString('en-GB')); // "25/12/2024, 15:30:00"

// Custom options: only date, long format
console.log(eventDate.toLocaleString('en-US', { year: 'numeric', month: 'long', day: 'numeric' }));
// "December 25, 2024"

Each of these built-in formatting methods has its strengths and limitations:

toDateString() is quick and simple for basic, human-friendly date displays, but does not allow customization or localization;
toLocaleString() is highly flexible and supports localization and various formatting options, but its output can vary across browsers and environments;
toISOString() provides a universal, consistent format suitable for data interchange, but is not user-friendly for most audiences.

Understanding when to use each method will help you present dates clearly and appropriately in your applications.

Alt var klart?

Takk for tilbakemeldingene dine!

Seksjon 2. Kapittel 2