JavaScript .then()

Returns a new Promise object.

Syntax

Promise.prototype.then(resolvedPromiseCallback, rejectedPromiseCallback);

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The resolvedPromiseCallback function handles any resolved data from the previously fulfilled promise. The other argument, rejectedPromiseCallback, is optional and executes if the previous Promise was rejected.

Example

const myPromise = new Promise((resolve, reject) => {
  if (2 + 2 === 3) {
    resolve('Success!');
  } else {
    reject({
      errorType: 'ArithmeticError',
      message: "The numbers don't add up!",
    });
  }
});

myPromise.then(
  (result) => {
    console.log(result);
  },
  (reason) => {
    console.log(`${reason.errorType}: ${reason.message}`); // ArithmeticError: The numbers don't add up!
  }
);

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Codebyte Example

The following example shows a .then() method executed for a successful result only by passing the resolve argument as the callback function.

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