Working with TypeScript Promises

Working with TypeScript Promises

Promises are an important part of any software project. They are used to handle asynchronous operations, and allow us to write code that is both efficient and maintainable. When working with TypeScript, you have the option of using either Promise or async/await syntax. Here we’ll explore how to use Promises in TypeScript, as well as some tips and tricks for making your code more elegant.

Creating a Promise in TypeScript

Creating a Promise in TypeScript is similar to creating one in JavaScript, except that all of your types need to be explicitly defined. The basic structure is as follows:

let promise = new Promise<string>((resolve, reject) => {
	// Do something asynchronous
	if (success) {
		resolve('Success!');
	} else {
		reject('Error!');
	}
});

In this example, we create a promise that resolves with a string when it succeeds, and rejects with another string when it fails. We can also specify an optional type argument when creating a Promise in TypeScript, which can be used to tell us what type of object our Promise will resolve with. For example, if we wanted to resolve with a number instead of a string, we could modify the code above to look like this:

let promise = new Promise<number>((resolve, reject) => {
	// Do something asynchronous
	if (success) {
		resolve(1);
	} else {
		reject(0);
	}
});

Consuming a Promise in TypeScript

Once we have created a Promise in TypeScript, we can consume the results with the .then() method. This method takes two functions as arguments, one for when the promise succeeds and one for when the promise fails. For example, if we want to use the promise from the example above we could do so like this:

promise.then((result) => {
	// Do something with result
}, (error) => {
	// Handle error
});

Conclusion

Promises are a powerful and useful tool in any language, and TypeScript is no exception. With the explicit typing available in TypeScript, we can make sure that our code is robust and easy to maintain. With a few simple lines of code, we can create and consume Promises to manage asynchronous operations in our applications.