Promise.resolve()

The Promise.resolve(value) method returns a Promise object that is resolved with the given value. If the value is a thenable (i.e. has a "then" method), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value.

Syntax

Promise.resolve(value);
Promise.resolve(promise);
Promise.resolve(thenable);

Parameters

value

Argument to be resolved by this Promise. Can also be a Promise or a thenable to resolve.

Return value

A Promise that is resolved with the given value.

Description

The static Promise.resolve function returns a Promise that is resolved.

Examples

Using the static Promise.resolve method

Promise.resolve("Success").then(function(value) {
  console.log(value); // "Success"
}, function(value) {
  // not called
});

Resolving an array

var p = Promise.resolve([1,2,3]);
p.then(function(v) {
  console.log(v[0]); // 1
});

Resolving another Promise

var original = Promise.resolve(true);
var cast = Promise.resolve(original);
cast.then(function(v) {
  console.log(v); // true
});

Resolving thenables and throwing Errors

// Resolving a thenable object
var p1 = Promise.resolve({ 
  then: function(onFulfill, onReject) { onFulfill("fulfilled!"); }
});
console.log(p1 instanceof Promise) // true, object casted to a Promise

p1.then(function(v) {
    console.log(v); // "fulfilled!"
  }, function(e) {
    // not called
});

// Thenable throws before callback
// Promise rejects
var thenable = { then: function(resolve) {
  throw new TypeError("Throwing");
  resolve("Resolving");
}};

var p2 = Promise.resolve(thenable);
p2.then(function(v) {
  // not called
}, function(e) {
  console.log(e); // TypeError: Throwing
});

// Thenable throws after callback
// Promise resolves
var thenable = { then: function(resolve) {
  resolve("Resolving");
  throw new TypeError("Throwing");
}};

var p3 = Promise.resolve(thenable);
p3.then(function(v) {
  console.log(v); // "Resolving"
}, function(e) {
  // not called
});

Specifications

Browser compatibility

To contribute to this compatibility data, please write a pull request against this file: https://github.com/mdn/browser-compat-data/blob/master/javascript/promise.json.

See also

• Promise