How to use Typescript with native ES6 Promises

Question

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'"

Answer 1

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.

Answer 2

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'

Answer 3

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.

Answer 4

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

Answer 5

这是最近的方法，上面的答案已经过时了：

typings install --global es6-promise

Answer 6

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); 
    }
);

Answer 7

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.

Answer 8

我不得不将@types/core-js降级到 9.36 才能让它与我的 tsconfig 中设置的"target": "es5"一起工作。

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

Answer 9

tsconfig.json 中的 typeorm 问题，添加以下属性："strictPropertyInitialization": false