WebMar 14, 2024 · Uncaught (in promise) TypeError: Cannot read properties of undefined (reading 'data') 这个错误消息表明在执行代码时发生了一个错误，该错误导致无法读取未定 … WebDec 16, 2013 · A promise can only succeed or fail once. It cannot succeed or fail twice, neither can it switch from success to failure or vice versa. If a promise has succeeded or failed and you later add a success/failure callback, the correct callback will be called, even though the event took place earlier.

クラス内のPromiseでundefined - Qiita

WebAug 23, 2024 · The initial promise resolves in 1 second (*), Then the .then handler is called (**), which in turn creates a new promise (resolved with 2 value). The next then (***) gets the result of the previous one, processes it (doubles) and passes it … WebMay 22, 2024 · After all, you get this error when calling the then () method on a Promise. And the TypeError indicates you are calling then () on undefined, which is a hint that the … bootrec windows 10 download

JavaScript Promises - W3Schools

WebBy definition, a promise is an objectthat encapsulates the result of an asynchronous operation. A promise object has a state that can be one of the following: Pending Fulfilled with a value Rejected for a reason In the beginning, the state of a promise is pending, indicating that the asynchronous operation is in progress. WebDec 15, 2024 · Promise states 2. result – This property can have the following values: undefined: Initially when the state value is pending. value: When resolve (value) is called. error: When reject (error) is called. These internal properties are code-inaccessible but they are inspectable. WebMay 22, 2024 · After all, you get this error when calling the then () method on a Promise. And the TypeError indicates you are calling then () on undefined, which is a hint that the Promise itself is undefined. The next step is to go and debug the … bootrec windows installations 0