Promise.reject()

Baseline

20157

Promise.reject() Promise

function resolved(result) {
  console.log("Resolved");
}

function rejected(result) {
  console.error(result);
}

Promise.reject(new Error("fail")).then(resolved, rejected);
// : Error: fail

Promise.reject(reason)

reason: Promise

Promise

Promise.reject Promise reason instanceof Error

Promise.reject() Promise Promise() resolve reject executor Promise.reject() new Promise((resolve, reject) => reject(reason))

Promise.resolve() Promise.reject() reason Promise Promise reason

Promise.reject()

Promise.reject(new Error("fail")).then(
  () => {
    // not called
  },
  (error) => {
    console.error(error); // Stacktrace
  },
);

Promise.resolve Promise.reject Promise reason Promise

const p = Promise.resolve(1);
const rejected = Promise.reject(p);
console.log(rejected === p); // false
rejected.catch((v) => {
  console.log(v === p); // true
});

Promise reject()

Promise.reject() Promise() console.log reject

class NotPromise {
  constructor(executor) {
    // The "resolve" and "reject" functions behave nothing like the
    // native promise's, but Promise.reject() calls them in the same way.
    executor(
      (value) => console.log("Resolved", value),
      (reason) => console.log("Rejected", reason),
    );
  }
}

Promise.reject.call(NotPromise, "foo"); // Logs "Rejected foo"


ECMAScript 2027 LanguageSpecification # sec-promise.reject

Promise

MDN

MDN 2025821

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