TypeScript: Promise static method gives error

TypeScript Version: 2.2.1

Steps to Reproduce:

Code used

let p = Promise.resolve([1, 2, 3]);
p.then(function (v) {
  console.log(v[0]); // 1
});

Both the compiler and vscode give this error.

src/main.ts(17,9): error TS2693: 'Promise' only refers to a type, but is being used as a value here.

Comment

I really think the TS compiler should be smart enough to figure out what “basic” types to include based off the field target from the TS configuration files, tsconfig.json

{
  "compilerOptions": {
    "module": "commonjs",
    "target": "es5",

Aside: As a developer, the last thing I care about is wasting my time with stupid typing errors, the entire typing system needs to be hidden from the developer.

package.json dependencies

 "devDependencies": {
    "@types/node": "^7.0.8",
    "ava": "^0.18.2",
    "browserify": "^14.1.0",
    "core-js": "^2.4.1",
    "cross-env": "^3.2.4",
    "cross-var": "^1.0.3",
    "gazeall": "^0.2.5",
    "husky": "^0.13.2",
    "lite-server": "^2.3.0",
    "npm-run-all": "^4.0.2",
    "nyc": "^10.1.2",
    "shx": "^0.2.2",
    "tachyons": "^4.6.2",
    "tap-summary": "^3.0.1",
    "tape-run": "^3.0.0",
    "tslint": "^4.5.1",
    "typedoc": "^0.5.7",
    "typescript": "^2.2.1",
    "typescript-formatter": "^5.1.2"
  },
  "dependencies": {
    "bunyan": "^1.8.8"
  },

About this issue

Original URL
State: closed
Created 7 years ago
Reactions: 15
Comments: 20 (5 by maintainers)

Most upvoted comments

You’re targeting ES5. Promises are not part of ES5. They’re part of ES6/ES2015.

To use Promises, you’ll need to adjust your lib option in tsconfig (see http://www.typescriptlang.org/docs/handbook/compiler-options.html).

+13

jwbay on Mar 25, 2017

@mhegazy yep

ps: little joke, don’t take it hard

bertolo1988 on May 23, 2017

> tslint --fix --type-check --project .

Error at src/Server.ts:102:20: 'Promise' only refers to a type, but is being used as a value here.
Error at src/Server.ts:133:20: 'Promise' only refers to a type, but is being used as a value here.
Error at src/Server.ts:149:20: 'Promise' only refers to a type, but is being used as a value here.
Error at src/Server.ts:165:20: 'Promise' only refers to a type, but is being used as a value here.

my tsconfig.json

{
    "compilerOptions": {
        "module": "commonjs",
        "target": "es6",
        "outDir": "dist",
        "rootDirs": [
            "src",
            "test"
        ],
        "sourceMap": true,
        "declaration": true
    },
    "exclude": [
        "node_modules",
        "dist"
    ]
}

My code looks like:

  function myFunction(): Promise<number>{
       return new Promise((resolve,reject)=>{
          resolve(3);
       })
   }

bertolo1988 on Apr 4, 2017

Still having this issue; these little errors are annyoing

HunderlineK on Apr 22, 2018

Try to add : "lib": [ "es6", "dom" ] to compilerOptions, then close the file and open again, just for refresh …

worked for my project…

oshri551 on May 4, 2017

I had the same issue. Reverting to 2.2.0 solved it for me.

DogAndHerDude on Apr 4, 2017