.then() or .catch()
To synchronously determine a JavaScript Promise’s state, you can inspect its properties and methods. In particular, you can check if the Promise has the .then() or .catch() method, as these methods are added to a Promise object when it is created.
Example: In this example, we will see how to synchronously determine a JavaScript Promise’s state by using the .then and .catch methods.
Javascript
const myPromise = new Promise((resolve, reject) => { setTimeout(() => { resolve("Successfull"); }, 1000); }); async function checkPromiseState() { try { const result = await myPromise; console.log("Promise is pending or fulfilled."); // Handle the fulfilled state here } catch (error) { console.log("Promise is rejected."); } } checkPromiseState(); |
Explanation
- In this example, we create a Promise myPromise and check for the existence of the .then() and .catch() methods.
- If the .then() method is present, the Promise is pending or fulfilled.
- If the .catch() method is present, the Promise is rejected.
Output:
Promise is pending or fulfilled.
How to Synchronously determine a JavaScript Promise’s State
Handling asynchronous operations in JavaScript can be challenging. However, Promises has made this task easier by providing a more elegant and better error management solution. Although Promise-based code is primarily designed to work asynchronously, there may be instances where you need to synchronously determine a Promise’s state for various reasons. In this article, we’ll explore how to do just that.
A Promise represents a value that might not be available yet but will be at some point in the future. It has three states:
- Pending: It is the state when the Promise is created and hasn’t been resolved or rejected yet.
- Fulfilled: The Promise has successfully resolved with a value.
- Rejected: The Promise has encountered an error or exception during its execution of code.
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