Ggtcf

Sort of trying to figure out how asynchronous stuff works in typescript and when I run my compiler it yields this error. Here is the code I'm trying to compile:

Printer.ts

export class Printer
 
 public static printString(string: string, callback): void
 
 setTimeout(
 () => 
 console.log(string)
 callback()
 ,
 Math.floor(Math.random() * 100) + 1
 )
 

 public static printStringWithPromise(string: string): Promise<void>
 
 return new Promise<void> ((resolve, reject) => 
 setTimeout(
 () => 
 console.log(string)
 resolve()
 ,
 Math.floor(Math.random() * 100) + 1
 )
 )
 

Main.ts

import Printer from './Printer';


class App

 public static run(): void
 
 Printer.printStringWithPromise("A")
 .then(() => Printer.printStringWithPromise("B"))
 .then(() => Printer.printStringWithPromise("C"))
 



App.run();

Then I just run tsc src/Main.ts --outDir out/ and it throws at me the above-mentioned error. What am I doing wrong?

In your tsconfig compiler options, check your --target and/or --lib. The Promise constructor only exists for ES2015 and later. Good luck!

By default, TypeScript includes only the es3 library during compilation, but promises only came with es6 (aka es2015). Thus, you'll have to include es6 in the tsconfig.json#compilerOptions#lib array - minimal example below.

tsconfig.json

 "compilerOptions": 
 "lib": ["es6"]
 ,
 "files": ["index.ts"]

index.ts

const prom = new Promise(resolve => resolve('hello world'));

test script

npm i typescript
tsc # <- should not throw any error