Description: The `Promise.then` method is a fundamental function in asynchronous programming in JavaScript and TypeScript, allowing for the handling of a promise’s result. This method is used to add handlers that execute when the promise is fulfilled (resolved) or rejected. The basic syntax of `then` is `promise.then(onFulfilled, onRejected)`, where `onFulfilled` is a function that runs if the promise resolves successfully, and `onRejected` is the function that runs if the promise is rejected. This approach allows for chaining multiple asynchronous operations in a more readable and structured manner, facilitating error management and data flow. Additionally, `Promise.then` returns a new promise, enabling the chaining of multiple `then` calls, creating a sequence of asynchronous operations. This method is essential for working with APIs, handling events, and performing tasks that require waiting, such as loading data from a server or executing code after certain conditions are met. In TypeScript, the use of `Promise.then` is complemented by the ability to type the success and error functions, enhancing code safety and clarity.
