Build an error handler for Javascript Promises(async await)
If you are a javascript developer, you may have used async and await, I know its simple to use and you love to. No more callbacks or .then() chain, just like synchronous javascript. but you may also have faced runtime errors/exceptions and you endup wrapping everything inside try.. catch... but that seems a lot of work. In this article, I will explain how you can add a custom function for your promise.
We all use async and await and we love to because its simple and no more then chains. but you might run into UnhandledPromiseRejectionWarning or Uncaught (in promise) Error and then You begin to wrap every piece of code using try.. catch.., Its fine for 1 or 2 async await but if you have a lot then that seems a lot of work. but what if I told you that you can write your custom promise error handler and reuse it whenever you need it.
Solution :
const asyncHandler = fn => async (...args) => {
try {
await fn(...args);
} catch (err) {
console.error(err);
}
};It takes all types of functions with any number of arguments. then in your code, use it like this:
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
const yourFunction = async () => {
await sleep(4000);
throw 'there was something wrong';
return 'success';
}
(async ()=> {
await yourFunction(); // will cause the uncaught error
await asyncHandler(yourFunction)(); // will handle the error properly
})();and if you need the result of the function, you can:
function sleep(ms) {
return new Promise(resolve => setTimeout(resolve, ms));
}
const yourFunction = async () => {
await sleep(4000);
return 'success';
}
(async ()=> {
const result = await asyncHandler(yourFunction)();
console.log(result);
})();and if you want custom error handling, you can just put your logic in the handler function like this :
const asyncHandler = (fn) => async (...args) => {
try {
await fn(...args);
} catch (err) {
console.error(err);
const errors = {
message: "Internal Sever Error",
error: err,
};
//you may want to add more checks here using instanceof
return errors;
}
};That's all, you can customize it as per your logic and need but the aim here is to get rid of repetitive try catch blocks and make it more simple and re-usable. If you find this tutorial helpful, please share it with your friends and colleagues. Don't forget to follow me :-)
Happy Coding ;-)
