Add ES2019 Object.fromEntries function

[saschanaz]

Search Terms

fromEntries

Suggestion

lib: es2019 should add Object.fromEntries() type.

Use Cases

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries

Examples

Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

[iugo]

https://github.com/tc39/proposal-object-from-entries

[waynevanson]

HI Guys,

Is this live yet and if so, which version? I can't get it to find it as Property 'fromEntries' does not exist on type 'ObjectConstructor'.

What versions of TS and NODEJS should I be running to make this work?

[waynevanson]

The file is available in my node_modules under lib.es2019.object.d.ts but it won't read from it?

Any link to any issue regarding how to resolve a similar issue is welcomed.

/// <reference no-default-lib="true"/>


/// <reference lib="es2015.iterable" />

interface ObjectConstructor {
    /**
     * Returns an object created by key-value entries for properties and methods
     * @param entries An iterable object that contains key-value entries for properties and methods.
     */
    fromEntries<T = any>(entries: Iterable<readonly [PropertyKey, T]>): { [k in PropertyKey]: T };

    /**
     * Returns an object created by key-value entries for properties and methods
     * @param entries An iterable object that contains key-value entries for properties and methods.
     */
    fromEntries(entries: Iterable<readonly any[]>): any;
}

[waynevanson]

HI Guys,

Is this live yet and if so, which version? I can't get it to find it as Property 'fromEntries' does not exist on type 'ObjectConstructor'.

What versions of TS and NODEJS should I be running to make this work?

It looks to me that in tsconfig.json, the setting to use is target: "es2019" or greater. This means it won't work in all browsers and typescrcipt does no magic to use this.

[bennypowers]

this is what I did

declare global {
  interface ObjectConstructor {
    fromEntries(xs: [string|number|symbol, any][]): object
  }
}

const fromEntries = (xs: [string|number|symbol, any][]) =>
  Object.fromEntries ? Object.fromEntries(xs) : xs.reduce((acc, [key, value]) => ({...acc, [key]: value}), {})

[tsujp]

Extending @bennypowers to sort an object similar to this:

{
  foo: 'bar',
  baz: 'boo',
  alpha: 'beta',
}

use

Object.keys(input).sort().reduce((acc, cur) => ({ ...acc, [cur]: input[cur] }), {})

[caseyhoward]

I ended up just defining my own functions for what I needed. They're pretty gross since they use any, but they get the job done for me I think:

function fromEntries<T>(entries: [keyof T, T[keyof T]][]): T {
  return entries.reduce(
    (acc, [key, value]) => ({ ...acc, [key]: value }),
    <T>{}
  );
}

function toEntries<T>(obj: T): [keyof T, T[keyof T]][] {
  const entries: [string, any][] = Object.entries(obj);
  const entriesWithKeysLookedUp: [keyof T, T[keyof T]][] = entries.map(item => {
    const keyString = item[0];
    const value = item[1];
    return [<keyof T>keyString, value];
  });
  return entriesWithKeysLookedUp;
}

All I wanted to do was map an objects values. Ended up being way more annoying than it should have been. Does anyone know a better way? It's annoying that Object.entries returns [string, T] and not a keyof type since you know the first element in each of the array elements is a keyof something and not just a string.

[MrCheater]

@caseyhoward , Hi. I have a problem with the {} construct. TypeScript 3.8.3. http://www.typescriptlang.org/v2/en/play?useDefineForClassFields=true&allowUnreachableCode=true&allowUnusedLabels=true&downlevelIteration=true&target=99

Cannot use JSX unless the '--jsx' flag is provided.(17004)
'T' only refers to a type, but is being used as a value here.(2693)
JSX element 'T' has no corresponding closing tag.(17008)

Do you know the solution?

[javiermrz]

Go into tsconfig.json, and inside compilerOptions properties search for a property named lib. Add the string "esnext" in the array. It should look something like:

"lib": ["es2018", "dom", "esnext"]

[dmorenogogoleva]

Add ["esnext"] to the lib worked for me! Thank u

[mapurba]

Hi All,
I am seeing this issue with chrome version 70 line , Angular TS
tsconfig : "lib": [ "es2018", "dom", "esnext" ]
one thing to notice the vendor js in lazy loaded as the .

with the uses of Object.fromEntries in .ts throws the same error in chrome 70 line .

case .ts : main.ts:12 TypeError: Object.fromEntries is not a function at new AppComponent (app.component.ts:15) at NodeInjectorFactory.AppComponent_Factory [as factory] (app.component.ts:18) at getNodeInjectable (core.js:5993) at instantiateRootComponent (core.js:12873)

case Vendor : VM547 vendor.js:98199 Uncaught TypeError: Object.fromEntries is not a function at Module.<anonymous> (VM547 vendor.js:98199) at i (VM547 vendor.js:98199) at push../node_modules/@ckeditor/ckeditor5-build-decoupled-document/build/ckeditor.js (VM547 vendor.js:98199) at VM547 vendor.js:98199 at VM547 vendor.js:98199 at Object../node_modules/@ckeditor/ckeditor5-build-decoupled-document/build/ckeditor.js (VM547 vendor.js:98199) at __webpack_require__ (VM542 runtime.js:85) at __webpack_require__ (VM542 runtime.js:85) at Module../src/app/shared/shared.module.ts (VM545 main.js:2147)

what is the right match so that all the dependency can be added in compile ?

but adding this to the polyfills make it work for all the cases .
import "core-js/es/object/from-entries";

ame right ?

*platform is web .

intention is to support the newer libs for older codebase dependency .

Thanks ,
Apurba M.

[sadeghmasoomi]

go to "tsconfig.json" and adding :

"lib": ["es2019"];