As of February 7, 2018
Chrome 63+, Firefox 58+, and Opera 50+ support Promise.finally.
In Node.js 8.1.4+ (V8 5.8+), the feature is available behind the flag --harmony-promise-finally.
The Promise.prototype.finally ECMAScript Proposal is currently in stage 3 of the TC39 process.
In the meantime to have promise.finally functionality in all browsers; you can add an additional then() after the catch() to always invoke that callback.
Example:
myES6Promise.then(() => console.log('Resolved'))
.catch(() => console.log('Failed'))
.then(() => console.log('Always run this'));
JSFiddle Demo: https://jsfiddle.net/9frfjcsg/
Or you can extend the prototype to include a finally() method (not recommended):
Promise.prototype.finally = function(cb) {
const res = () => this;
const fin = () => Promise.resolve(cb()).then(res);
return this.then(fin, fin);
};
JSFiddle Demo: https://jsfiddle.net/c67a6ss0/1/
There's also the Promise.prototype.finally shim library.
