Property 'allSettled' does not exist on type 'PromiseConstructor'.ts(2339)

Question

I\'m trying to use the Promise.allSettled API with TypeScript. Code here:

server.test.ts:

it(\'shou         


        

Answer 1

It's ES2020 and at Stage 4, so not available everywhere without a polyfill. It got typed and merged into TS. Try installing the latest @types/node package and see if that pulls it in.

Update: Looks like it will be adding es2020.promise to the libs, when it does land.

Update: npm i typescript@3.8.0-beta woot woot!

Answer 2

The types for Promise.allSettled() were only merged in January, and will apparently be released in TypeScript 3.8.

As an interim solution, you can declare a mock-ish type for the function yourself:

declare interface PromiseConstructor {
    allSettled(promises: Array<Promise<any>>): Promise<Array<{status: 'fulfilled' | 'rejected', value?: any, reason?: any}>>;
}

Answer 3

To get this running on Linux, I needed the latest typescript version:

sudo npm install -g typescript@latest

Then in your tsconfig you currently need the ES2020.Promise lib. My full tsconfig:

{
  "compilerOptions": {
    "sourceMap": true,
    "module": "commonjs",
    "target": "es5",
    "jsx": "react",
    "esModuleInterop": true,
    "allowJs": true,
    "outDir": "./dist",
    "lib": [
      "ES2020.Promise",
    ]
  },
  "include": [
    "./src"
  ],
  "exclude": [
    "./node_modules",
    "./build"
  ],
  "compileOnSave": true,
  "parserOptions": {
    "ecmaFeatures": {
      "jsx": true
    }
  }
}

Usage: const results = await Promise.allSettled(BatchOfPromises);