ES7 Object.entries() in TypeScript not working

Question

I have an issue with transpiling ES7 code with TypeScript. This code:

const sizeByColor = {     red: 100,     green: 500, };  for ( const [ color, size ] of Object.entries(sizeByColor) ) {     console.log(color);     console.log(size); } 

gives the error:

TypeError: Object.entries is not a function

TypeScript v2.0.3

tsconfig.json:

{ "compilerOptions": {     "module": "commonjs",     "target": "es6",     "noImplicitAny": true,     "noEmitOnError": true,     "outDir": "dist",     "allowSyntheticDefaultImports": true,     "experimentalDecorators": true,     "pretty": true,     "lib": [ "es2017" ], }, "exclude": [     "node_modules" ], "include": [     "./node_modules/@types/**/*.d.ts",     "./src/**/*.ts" ] } 

I want to iterate trough object with Object.entries(), so I assigned internal definitions "lib": [ "es2017" ], but still, typescript wont allow me to transpile it.

Answer 1

I can reproduce your problem when I have a global compiler but not a local one in the ./node_modules.

In my case compiler just does not know which tsconfig.json file to use. Pointing it to a particular tsconfig.json file helps:

tsc  --project ./tsconfig.json 

I have also added dom option to the lib, because es2017 does not recognize console:

"lib": [     "es2017",     "dom" ] 

Answer 2

If you don't want to include the full set of ECMAScript 2017 (ES8) in your set of libraries, then you can also use es2017.object to just satisfy the resolution of Object.entries and related.

Here is a minimal working example:

src/index.ts

const sizeByColor = {   red: 100,   green: 500, };  for (const [color, size] of Object.entries(sizeByColor)) {   console.log(color);   console.log(size); } 

tsconfig.json

{   "compilerOptions": {     "lib": ["dom", "es2016", "es2017.object"],     "rootDir": "src",     "target": "es6",     "outDir": "dist"   },   "exclude": [     "node_modules"   ] } 

Note: If "target" is set to "es6", then TypeScript uses by default the following "lib" entries (if none are specified): ["dom", "dom.iterable", "es6", "scripthost"].

The library defaults get overwritten when setting "lib" manually, that's why I needed to add "dom" (to use console.log in my code) and "es6" to demonstrate the usage of ES6 and partial ES8 ("es2017.object").

Source: TypeScript Compiler Options