The Promise is an object that represents either completion or failure of a user task. A promise in JavaScript can be in three states pending, fulfilled or rejected.
The main advantage of using a Promise in JavaScript is that a user can assign callback functions to the promises in case of a rejection or fulfillment of Promise. As the name suggests a promise is either kept or broken. So, a promise is either completed(kept) or rejected(broken).
Promise resolve() method:
Promise.resolve() method in JS returns a Promise object that is resolved with a given value. Any of the three things can happend:
- If the value is a promise then promise is returned.
- If the value has a “then” attached to the promise, then the returned promise will follow that “then” to till the final state.
- The promise fulfilled with its value will be returned.
Syntax:
Promise.resolve(value);
Parameters:
Value to be resolved by this Promise.
Return Value:
Either the promise of the promise fulfilled with its value is returned.
Examples:
<script> var promise = Promise.resolve(17468); promise.then(function(val) { console.log(val); }); //Output: 17468 </script> |
Output:
17468
Resolving an array:
<script> const promise = new Promise((resolve, reject) => { setTimeout(() => { resolve([89, 45, 323]); }, 5000); }); promise.then(values => { console.log(values[1]); }); </script> |
Output:
45
Resolving another Promise:
<script> const promise = Promise.resolve(3126); const promise1 = new Promise((resolve, reject) => { setTimeout(() => { promise.then(val => console.log(val)); }, 5000); }); promise1.then(vals => { console.log(vals); }); </script> |
Output:
3126
