In Promise,rejectandcatchThere are two ways to deal with asynchronous operation failures. They have some important differences:
reject：
rejectis a method of the Promise instance to explicitly transfer the Promise state frompendingChange torejected, and pass a reason for rejection (usually an Error object or a value that describes the failure).
Once the Promise entersrejectedThe status will trigger the Promise chain to follow immediately.rejectThe first one behindcatchMethod or the nextthenFailure handling function in the method (if any).
Example:
let promise = new Promise((resolve, reject) => {
reject(new Error('Something went wrong'));
});
(error => {
(error);
});catch：
catchis a method of a Promise instance that registers functions that catch exceptions in the Promise chain. It only captures the Promise status asrejectedScenario.
catchMethod receives a callback function, which enters in PromiserejectedThe status is called and can be accessedrejectThe reason for the rejection of the pass.
Example:
let promise = new Promise((resolve, reject) => {
throw new Error('Something went wrong');
});
(error => {
(error);
});Summary of the differences:
Trigger timing：
-
rejectActively call during the execution of the Promise and explicitly change the Promise state torejected。 -
catchis a method registered in the Promise chain, used to capture and reachrejectedPromise of status.
usage：
-
rejectUsed to handle errors during the execution of the Promise and pass them to subsequent handlers. -
catchA callback function used to register errors in the Promise chain.
Chain call：
-
rejectIt is an operation in the Promise executor function, and cannot be likecatchSame chain call, because it does not return a Promise object. -
catchCan be called in a chain, allowing possible errors in multiple steps in the Promise chain.
In practical applications, it is usually recommended to usecatchMethods to handle exceptions in the Promise chain because it can more clearly separate error handling from chain calls, making the code more readable and maintained.
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