javascript class, method that returns a possible error to handle it

Question

I have a class, I would like an error method to return a way to handle it from the object

class MyClass {
On(value){
     try{
     throw new Error("Massimo due candidati");
      }
      catch(e){
              console.log(e.name, e.message); //Error, I'm Evil
      }
}
}

If I create an object of the class how can I handle the error in a similar way?

var obj = new MyClass();
obj.on(value, err=> {
if (err) {
    onError(err.message);
  }else{
    console.log("Inserimento ok");
  }
});

Thanks for your attention.

CertainPerformance · Accepted Answer · 2020-05-02 10:39:24Z

1

When .on is called, push the callback to an array of callbacks stored by the object. Then, whenever whatever triggers the .on runs, iterate through all callbacks in the array and invoke them (and possibly pass an error argument too):

class MyClass {
  onCallbacks = [];
  on(someArg, callback) {
    this.onCallbacks.push(callback);
  }
  invokeOK() {
    this.onCallbacks.forEach((callback) => {
      callback();
    });
  }
  invokeError() {
    this.onCallbacks.forEach((callback) => {
      callback(new Error('foo'));
    });
  }
}

const onError = console.error;
const obj = new MyClass();
obj.on('value', err => {
  if (err) {
    onError(err.message);
  } else {
    console.log("Inserimento ok");
  }
});

obj.invokeError();
obj.invokeOK();

answered May 2, 2020 at 10:39

CertainPerformance

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Comments

Gaetano De Gregorio · Accepted Answer · 2020-05-02 12:30:52Z

thanks for your help. I think in my head I wanted to do this ...

class MyClass {
  onCallbacks = [];
  on(someArg, callback) {
    if (someArg != 'value') {
        this.onCallbacks.push(callback);
    }else{
    console.log("start ok");
    }
  }
  invokeOK() {
  //if (this.onCallbacks.length==0){return;}
    this.onCallbacks.forEach((callback) => {
      callback();
    });
  }
  invokeError() {
    this.onCallbacks.forEach((callback) => {
      callback(new Error('foo'));
    });
  }
}

const onError = console.error;
const obj = new MyClass();

obj.on('value', err => {
  if (err) {
    onError(err.message);
    console.log(err.message);
  }
});
obj.invokeError();
obj.invokeOK();

If it seems wrong to you as a process, let me know.

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