How to use Typescript with native ES6 Promises

I'm a complete beginner to Typescript and am wondering if it's possible to use ES6 promises in Typescript and what I would have to do to get them to work. I'm running node 0.11.14 and am getting an error during compilation "Cannot find name 'Promise'"

The current lib.d.ts doesn't have promises in it defined so you need a extra definition file for it that is why you are getting compilation errors.

You could for example use (like @elclanrs says) use the es6-promise package with the definition file from DefinitelyTyped: es6-promise definition

You can then use it like this:

var p = new Promise<string>((resolve, reject) => { 
    resolve('a string'); 
});

edit You can use it without a definition when targeting ES6 (with the TypeScript compiler) - Note you still require the Promise to exists in the runtime ofcourse (so it won't work in old browsers :)) Add/Edit the following to your tsconfig.json :

"compilerOptions": {
    "target": "ES6"
}

edit 2 When TypeScript 2.0 will come out things will change a bit (though above still works) but definition files can be installed directly with npm like below:

npm install --save @types/es6-promise - source

edit3 Updating answer with more info for using the types.

Create a package.json file with only { } as the content (if you don't have a package.json already. Call npm install --save @types/es6-promise and tsc --init. The first npm install command will change your package.json to include the es6-promise as a dependency. tsc --init will create a tsconfig.json file for you.

You can now use the promise in your typescript file var x: Promise<any>;. Execute tsc -p . to compile your project. You should have no errors.

Alternative #1

Use the target and lib compiler options to compile directly to es5 without needing to install the es6-shim. (Tested with TypeScript 2.1.4). In the lib section, use either es2016 or es2015.promise.

// tsconfig.json
{
    "compilerOptions": {
        "target": "es5",
        "lib": [
            "es2015.promise",
            "dom"
        ]
    },
    "include": [
        "src/**/*.ts"
    ],
    "exclude": [
        "node_modules"
    ]
}

Alternative #2

Use NPM to install the es6-shim from the types organization.

npm install @types/es6-shim --save-dev

Alternative #3

Before TypeScript 2.0, use typings to install the es6-shim globally from DefinitelyTyped.

npm install typings --global --save-dev
typings install dt~es6-shim --global --save-dev

The typings option uses npm to install typings globally and then uses typings to install the shim. The dt~ prefix means to download the shim from DefinitelyTyped. The --global option means that the shim's types will be available throughout the project.

See also

https://github.com/Microsoft/TypeScript/issues/7788 - Cannot find name 'Promise' & Cannot find name 'require'

As of TypeScript 2.0 you can include typings for native promises by including the following in your tsconfig.json

"compilerOptions": {
    "lib": ["es5", "es2015.promise"]
}

This will include the promise declarations that comes with TypeScript without having to set the target to ES6.

If you use node.js 0.12 or above / typescript 1.4 or above, just add compiler options like:

tsc a.ts --target es6 --module commonjs

More info: https://github.com/Microsoft/TypeScript/wiki/Compiler-Options

If you use tsconfig.json, then like this:

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es6"
    }
}

More info: https://github.com/Microsoft/TypeScript/wiki/tsconfig.json

This the most recent way to do this, the above answer is outdated:

typings install --global es6-promise

Using native ES6 Promises with Typescript in Visual Studio 2015 + Node.js tools 1.2

No npm install required as ES6 Promises is native.

Node.js project -> Properties -> Typescript Build tab ECMAScript version = ECMAScript6

import http = require('http');
import fs = require('fs');

function findFolderAsync(directory : string): Promise<string> {

    let p = new Promise<string>(function (resolve, reject) {

        fs.stat(directory, function (err, stats) {

            //Check if error defined and the error code is "not exists"
            if (err && err.code === "ENOENT") {
                reject("Directory does not exist");
            }
            else {
                resolve("Directory exists");
            }
        });

    });
    return p;
}

findFolderAsync("myFolder").then(

    function (msg : string) {
        console.log("Promise resolved as " + msg); 
    },
    function (msg : string) {
        console.log("Promise rejected as " + msg); 
    }
);

A. If using "target": "es5" and TypeScript version below 2.0:

typings install es6-promise --save --global --source dt

B. If using "target": "es5" and TypeScript version 2.0 or higer:

"compilerOptions": {
    "lib": ["es5", "es2015.promise"]
}

C. If using "target": "es6", there's no need to do anything.

I had to downgrade @types/core-js to 9.36 to get it to work with "target": "es5" set in my tsconfig.

"@types/core-js": "0.9.36",

typeorm problems in tsconfig.json, add the following property : "strictPropertyInitialization": false