Unable to handle errors in javascript promise

Question

Why doesn't it run the code "console.log(err)" below? but instead returns "TypeError: Cannot create property 'uncaught' on string 'error in promise'"

function abc() {
    throw "error in promise";
    return 123;
};
abc().catch(function(err) {
    console.log(err)
}).then ( abcMessage =>
    console.log(abcMessage)
)

Don’t throw strings; throw errors. new Error("error in promise") — Ry-
– Ry- ♦, Commented Apr 14, 2017 at 1:54
thanks! amended it to new Error("error in promise") and the error is gone but now instead of running console.log(err) it throws the error Error: error in promise before it reaches console.log(err) — Stanley
– Stanley, Commented Apr 14, 2017 at 1:58

KevBot · Accepted Answer · 2017-04-14 04:43:29Z

2

.then and .catch require a Promise to be constructed. You are not returning a promise. The promise callback (executor) takes two arguments, a resolver, and a rejecter. Depending on what happens in the code, you may need to call resolve if everything goes right, or reject if something goes wrong.

function abc() {
  return new Promise(function(resolve, reject) {
    reject(123)
  });
};


abc()
  .catch(err => {
    console.log(err);
    return err;
  })
  .then(abcMessage => {
    console.log(abcMessage)
  });

new Error("error in promise")

edited Apr 14, 2017 at 4:43

answered Apr 14, 2017 at 2:03

KevBot

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1 Comment

user663031 Over a year ago

What you call the "promise callback" actually has an official name, which is executor.

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