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106 lines
2.8 KiB
Markdown
106 lines
2.8 KiB
Markdown
# Combine-Promises
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[](https://www.npmjs.com/package/combine-promises)
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[](https://github.com/slorber/combine-promises/actions/workflows/main.yml)
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Like `Promise.all([])` but for objects.
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```ts
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import combinePromises from 'combine-promises';
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const { user, company } = await combinePromises({
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user: fetchUser(),
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company: fetchCompany(),
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});
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```
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Why:
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- Insensitive to destructuring order
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- Simpler async functional code
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Features:
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- TypeScript support
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- Lightweight
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- Feature complete
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- Well-tested
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- ESM / CJS
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---
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# Sponsor
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**[ThisWeekInReact.com](https://thisweekinreact.com)**: the best newsletter to stay up-to-date with the React ecosystem:
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[](https://thisweekinreact.com)
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---
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## Install
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```
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npm install combine-promises
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// OR
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yarn add combine-promises
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```
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## TypeScript support
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Good, native and strict TypeScript support:
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- Return type correctly inferred from the input object
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- All object values should be async
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- Only accept objects (reject arrays, null, undefined...)
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```ts
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const result: { user: User; company: Company } = await combinePromises({
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user: fetchUser(),
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company: fetchCompany(),
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});
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```
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## Insensitive to destructuring order
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A common error with `Promise.all` is to have a typo in the destructuring order.
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```js
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// Bad: destructuring order reversed
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const [company, user] = await Promise.all([fetchUser(), fetchCompany()]);
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```
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This becomes more dangerous as size of the promises array grows.
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With `combinePromises`, you are using explicit names instead of array indices, which makes the code more robust and not sensitive to destructuring order:
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```js
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// Good: we don't care about the order anymore
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const { company, user } = await combinePromises({
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user: fetchUser(),
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company: fetchCompany(),
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});
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```
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## Simpler async functional code
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Suppose you have an object representing a friendship like `{user1: "userId-1", user2: "userId-2"}`, and you want to transform it to `{user1: User, user2: User}`.
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You can easily do that:
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```js
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import combinePromises from 'combine-promises';
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import { mapValues } from 'lodash'; // can be replaced by vanilla ES if you prefer
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const friendsIds = { user1: 'userId-1', user2: 'userId-2' };
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const friends = await combinePromises(mapValues(friendsIds, fetchUserById));
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```
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Without this library: good luck to keep your code simple.
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## Inspirations
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Name inspired by [combineReducers](https://redux.js.org/api/combinereducers) from Redux.
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