Native Support for Promises in Node.js

Question

Is there native support for promises in current versions of Node.js? Node.js uses the V8 engine. This JavaScript engine is also used by Chrome, and Chrome 32 has native support for promises. But I can't seem to get promises to work (natively) in Node.js. I've tried the following code in Chrome 32 and it works. ``` var promise = new Promise(function(resolve, reject) { // do a thing, possibly async, then… if ( 1===1 /* everything turned out fine */) { resolve("Stuff worked!"); } else { reject(Error("It broke")); } }); promise.then(function( message ) { console.log( message ); }, function( err ) { console.log( err ); }); ``` However, when I try this same code in Node.js, I get: ``` var promise = new Promise(function(resolve, reject) { ^ ReferenceError: Promise is not defined ``` This code is from the excellent tutorial: http://www.html5rocks.com/en/tutorials/es6/promises/

Accepted Answer

If node is using the same or later version of V8 that Chrome 32 uses then it is likely natively supported. Otherwise you will need to load 'es6-shim' (I recommend loading es5-shim first) I have no idea which version of V8 the current release of node is using.

On my node install

```
node --version
v0.10.24

node -e 'console.log(process.versions.v8);'
3.14.5.9
```

What version is Chrome V32 using? (I am using Chromium v27), so would have to find documentation, but possibly 3.22.24.16

Looking in `chrome://version/` seems to give the information

```
Chromium    27.0.1453.93 (Developer Build 200836) Built from source for Fedora release 19 (Schrödinger’s Cat)
OS  Linux 
WebKit  537.36 (Unknown URL@0)
JavaScript  V8 3.17.6.14
Flash   11.2 r202
User Agent  Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.93 Safari/537.36
Command Line     /usr/lib64/chromium-browser/chromium-browser --enable-plugins --enable-extensions --enable-user-scripts --enable-printing --enable-sync --auto-ssl-client-auth --flag-switches-begin --enable-sync-favicons --enable-full-history-sync --sync-keystore-encryption --flag-switches-end
Executable Path /usr/lib64/chromium-browser/chromium-browser
Profile Path    /home/graham/.config/chromium/Profile 1
Variations  b03ddc1f-2d9ef0cc
f9b252d0-fd526c81
ff3fc1a6-766fa2d
7f6da4bf-70d6abf1
75f7fb7e-611a9f49
262f996f-42d3ce07
24dca50e-455c9cca
ca65a9fe-91ac3782
3028188e-626278e
5e29d81-cf4f6ead
246fb659-6754d7b7
f296190c-72d8285f
4442aae2-4ad60575
75f0f0a0-a5822863
e2b18481-6e3b1976
e7e71889-e1cc0f14
```

And now from a Chrome install

```
Google Chrome   32.0.1700.107 (Official Build 248368) 
OS  Linux 
Blink   537.36 (@165586)
JavaScript  V8 3.22.24.17
Flash   12.0.0.44
User Agent  Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/32.0.1700.107 Safari/537.36
Command Line     /usr/bin/google-chrome-stable --flag-switches-begin --flag-switches-end
Executable Path /opt/google/chrome/google-chrome
Profile Path    /home/graham/.config/google-chrome/Default
Variations  b178bdde-887f97ea
24dca50e-837c4893
8d790604-9cb2a91c
5a3c10b5-e1cc0f14
244ca1ac-4ad60575
5e29d81-cf4f6ead
3ac60855-486e2a9c
246fb659-bd104136
f296190c-38939ee9
4442aae2-6e597ede
ed1d377-e1cc0f14
75f0f0a0-e1cc0f14
e2b18481-6e597ede
e7e71889-4ad60575
```

Native Support for Promises in Node.js

Solution

Problem