TS2304

error TS2304: Cannot find name ‘world’.

Broken Code ❌

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console.log(world.name);

Fixed Code ✔️

It can happen that TypeScript does not know about your global objects because those may be injected from an unknown runtime environment or third-party JavaScript library. The easiest way to let TypeScript know about this is to declare the ambience (ambient context):

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declare var world: {
  name: string;
};

console.log(world.name);

error TS2304: Cannot find name ‘Promise’

Broken Code ❌

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// ...

public load_prekey(prekey_id: number): Promise<Proteus.keys.PreKey> {
  return new Promise((resolve) => {
    resolve(42);
  });
}

// ...

Fixed Code ✔️

Install es6-promise type definitions with the typings tool.

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typings install dt~es6-promise --global --save

Adding the following line to the beginning of every file using definitions from es6-promise.

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/// <reference path='es6-promise.d.ts' />

...

public load_prekey(prekey_id: number): Promise<Proteus.keys.PreKey> {
  return new Promise((resolve) => {
    resolve(42);
  });
}

...

error TS2304: Cannot find name ‘Promise’

Broken Code ❌

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const UUID = require('uuidjs');

Fixed Code ✔️

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npm install @types/node --save-dev

error TS2304: Cannot find name ‘FC’.

Broken Code ❌

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import React from 'react';

const App: FC = (): JSX.Element => {
  return <></>;
};

Fixed Code ✔️

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import React, {FC} from 'react';

const App: FC = (): JSX.Element => {
  return <></>;
};