🔰recoverable errors

⭐️ 重點

• .catch() callback is for：

  • reporting errors

  • handling errors

  • recovering from errors ⭐️

• .catch() callback can throw a new error, but if it returns normally, than that return value is used to resolve (fulfill) the associated Promise, and the error stops propagating.

💈範例

// recover from errors
asyncOperation()
    .then(doStage2)
    
    // ⭐️ catch recoverable errors from stage 2
    // ---------------------------------------------------------
    // if `recoverableErrors` returns normally, its return value
    // is passed to `doStage3` and continues normally.
    .catch(recoverableErrors)     
    
    .then(doStage3) 
    .then(doStage4) 
    .catch(stage3And4Errors);
    
// recover from network problems
queryDatabase() 

     // ⭐️ wait and retry (`wait` is fictional)
    .catch(e => wait(500).then(queryDatabase))
    
    .then(displayTable) 
    .catch(displayDatabaseError);