how to use top level async await with typescript?

Question

I've a typescript project, when i use await xxx.someAsyncMethod(..) at the top level, typescript linter shows,

Top-level 'await' expressions are only allowed when the 'module' option is set to 'esnext' or 'system', and the 'target' option is set to 'es2017' or higher.

so I'll change the module to esnext "module": "esnext"

and i'll go ahead and try running the program npx ts-node app/app.ts

then console informs me

(node:15509) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
Cannot use import statement outside a module

upon setting the type to module in package.json "type": "module" when i run the program the console out puts

TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" for /Users/apple/Desktop/source_given_to_me/Git/bots/wab/app/app.ts
    at Loader.defaultGetFormat [as _getFormat] (internal/modules/esm/get_format.js:65:15)
    at Loader.getFormat (internal/modules/esm/loader.js:113:42)
    at Loader.getModuleJob (internal/modules/esm/loader.js:244:31)
    at Loader.import (internal/modules/esm/loader.js:178:17)

what can be done so i can get away with using top level async await?

EDIT: my redis.ts file

import * as pm from "child_process"
var prc:pm.ChildProcess;

async function startRedis(path:string): Promise<boolean> {
    return new Promise((resolve) => {
        console.log('starting redis')
        var rp = pm.spawn(path)
        rp.stdout.on("data", (data) => {
            console.log(data)
            console.log('redis fired up')
            prc= rp
            resolve(true)
        })
        rp.stderr.on("data", (data) => {
            console.log(data)
            console.log('redis failed to start')
            resolve(false)
        })
    })
}

function active():boolean{
    return prc?!prc.killed:false
}

async function stopRedis(): Promise<boolean> {
    return new Promise(
        (resolve)=>{
            if(prc){
                resolve(prc.kill("SIGTERM"))
            } else {
                resolve(false)
            }
        }
    )
}


export const redis = {
    startRedis,
    stopRedis,
    active
}

my config.ts file (tsconfig.json is below)

export const config = {
    redisPath:'../r607/src/redis-server'
}

my app.ts file

import {config} from "./config.js"
import {redis} from "./redis.js"
//import * as pm from "child_process"

await redis.startRedis(config.redisPath)
if(!redis.active()){
    process.abort()
}

my tsconfig.json

{
  "compilerOptions": {
    /* Visit https://aka.ms/tsconfig.json to read more about this file */

    /* Basic Options */
    // "incremental": true,                   /* Enable incremental compilation */
    "target": "esnext",                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
    "module": "ESNext",                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
    // "lib": [],                             /* Specify library files to be included in the compilation. */
    // "allowJs": true,                       /* Allow javascript files to be compiled. */
    // "checkJs": true,                       /* Report errors in .js files. */
    // "jsx": "preserve",                     /* Specify JSX code generation: 'preserve', 'react-native', or 'react'. */
    // "declaration": true,                   /* Generates corresponding '.d.ts' file. */
    // "declarationMap": true,                /* Generates a sourcemap for each corresponding '.d.ts' file. */
    // "sourceMap": true,                     /* Generates corresponding '.map' file. */
    // "outFile": "./",                       /* Concatenate and emit output to single file. */
     "outDir": "./build",                        /* Redirect output structure to the directory. */
    // "rootDir": "./",                       /* Specify the root directory of input files. Use to control the output directory structure with --outDir. */
    // "composite": true,                     /* Enable project compilation */
    // "tsBuildInfoFile": "./",               /* Specify file to store incremental compilation information */
    // "removeComments": true,                /* Do not emit comments to output. */
    // "noEmit": true,                        /* Do not emit outputs. */
    // "importHelpers": true,                 /* Import emit helpers from 'tslib'. */
    // "downlevelIteration": true,            /* Provide full support for iterables in 'for-of', spread, and destructuring when targeting 'ES5' or 'ES3'. */
    // "isolatedModules": true,               /* Transpile each file as a separate module (similar to 'ts.transpileModule'). */

    /* Strict Type-Checking Options */
    "strict": true,                           /* Enable all strict type-checking options. */
    // "noImplicitAny": true,                 /* Raise error on expressions and declarations with an implied 'any' type. */
    // "strictNullChecks": true,              /* Enable strict null checks. */
    // "strictFunctionTypes": true,           /* Enable strict checking of function types. */
    // "strictBindCallApply": true,           /* Enable strict 'bind', 'call', and 'apply' methods on functions. */
    // "strictPropertyInitialization": true,  /* Enable strict checking of property initialization in classes. */
    // "noImplicitThis": true,                /* Raise error on 'this' expressions with an implied 'any' type. */
    // "alwaysStrict": true,                  /* Parse in strict mode and emit "use strict" for each source file. */

    /* Additional Checks */
    // "noUnusedLocals": true,                /* Report errors on unused locals. */
    // "noUnusedParameters": true,            /* Report errors on unused parameters. */
    // "noImplicitReturns": true,             /* Report error when not all code paths in function return a value. */
    // "noFallthroughCasesInSwitch": true,    /* Report errors for fallthrough cases in switch statement. */

    /* Module Resolution Options */
    // "moduleResolution": "node",            /* Specify module resolution strategy: 'node' (Node.js) or 'classic' (TypeScript pre-1.6). */
    // "baseUrl": "./",                       /* Base directory to resolve non-absolute module names. */
    // "paths": {},                           /* A series of entries which re-map imports to lookup locations relative to the 'baseUrl'. */
    // "rootDirs": [],                        /* List of root folders whose combined content represents the structure of the project at runtime. */
    // "typeRoots": [],                       /* List of folders to include type definitions from. */
    // "types": [],                           /* Type declaration files to be included in compilation. */
    // "allowSyntheticDefaultImports": true,  /* Allow default imports from modules with no default export. This does not affect code emit, just typechecking. */
    "esModuleInterop": true,                  /* Enables emit interoperability between CommonJS and ES Modules via creation of namespace objects for all imports. Implies 'allowSyntheticDefaultImports'. */
    // "preserveSymlinks": true,              /* Do not resolve the real path of symlinks. */
    // "allowUmdGlobalAccess": true,          /* Allow accessing UMD globals from modules. */

    /* Source Map Options */
    // "sourceRoot": "",                      /* Specify the location where debugger should locate TypeScript files instead of source locations. */
    // "mapRoot": "",                         /* Specify the location where debugger should locate map files instead of generated locations. */
    // "inlineSourceMap": true,               /* Emit a single file with source maps instead of having a separate file. */
    // "inlineSources": true,                 /* Emit the source alongside the sourcemaps within a single file; requires '--inlineSourceMap' or '--sourceMap' to be set. */

    /* Experimental Options */
    // "experimentalDecorators": true,        /* Enables experimental support for ES7 decorators. */
    // "emitDecoratorMetadata": true,         /* Enables experimental support for emitting type metadata for decorators. */

    /* Advanced Options */
    "skipLibCheck": true,                     /* Skip type checking of declaration files. */
    "forceConsistentCasingInFileNames": true  /* Disallow inconsistently-cased references to the same file. */
  }
}

Answer 1

Follow these steps:

• Add "type": "module" to your package.json.
• Replace "main": "index.js" with "exports": "./index.js" in your package.json.
• Update the "engines" field in package.json to Node.js 12: "node": "^12.20.0 || ^14.13.1 || >=16.0.0".
• Add "module": "ES2020" to your tsconfig.json.
• Use only full relative file paths for imports: import x from '.'; → import x from './index.js';.
• Remove namespace usage and use export instead.
• Optional but recommended, use the node: protocol for imports.
• You must use a .js extension in relative imports even though you're importing .ts files.

if you use ts-node use it like:

node --loader ts-node/esm ./entrypoint.ts

Edit: source gist

Answer 2

You can achieve the same results with this pattern:

async function main(): Promise<void> {
    const foo = await somePromise
    console.log(foo)
}

main()

Even though you aren't awaiting main, NodeJS won't exit until the event queue is empty. In other words, it won't exit while there are unresolved promises.