es-shims
promise.prototype.finally 
ES Proposal spec-compliant shim for Promise.prototype.finally. Invoke its "shim" method to shim Promise.prototype.finally if it is unavailable or noncompliant. Note: a global Promise must already exist: the es6-shim is recommended.
This package implements the es-shim API interface. It works in an ES3-supported environment that has Promise available globally, and complies with the proposed spec.
Most common usage:
var assert = require('assert');
var promiseFinally = require('promise.prototype.finally');
var resolved = Promise.resolve(42);
var rejected = Promise.reject(-1);
promiseFinally(resolved, function () {
assert.equal(arguments.length, 0);
return Promise.resolve(true);
}).then(function (x) {
assert.equal(x, 42);
});
promiseFinally(rejected, function () {
assert.equal(arguments.length, 0);
}).catch(function (e) {
assert.equal(e, -1);
});
promiseFinally(rejected, function () {
assert.equal(arguments.length, 0);
throw false;
}).catch(function (e) {
assert.equal(e, false);
});
promiseFinally.shim(); // will be a no-op if not needed
resolved.finally(function () {
assert.equal(arguments.length, 0);
return Promise.resolve(true);
}).then(function (x) {
assert.equal(x, 42);
});
rejected.finally(function () {
assert.equal(arguments.length, 0);
}).catch(function (e) {
assert.equal(e, -1);
});
rejected.finally(function () {
assert.equal(arguments.length, 0);
throw false;
}).catch(function (e) {
assert.equal(e, false);
});Tests
Simply clone the repo, npm install, and run npm test
Thanks
Huge thanks go out to @matthew-andrews, who provided the npm package name for v2 of this module. v1 is both in the original repo and preserved in a branch