https://github.com/oliverjash/express-fp
Type safe request handlers for Express. TypeScript compatible.
https://github.com/oliverjash/express-fp
Last synced: 3 months ago
JSON representation
Type safe request handlers for Express. TypeScript compatible.
- Host: GitHub
- URL: https://github.com/oliverjash/express-fp
- Owner: OliverJAsh
- Created: 2017-07-16T12:28:25.000Z (almost 8 years ago)
- Default Branch: master
- Last Pushed: 2018-10-31T10:43:55.000Z (over 6 years ago)
- Last Synced: 2025-03-18T01:42:40.296Z (3 months ago)
- Language: TypeScript
- Homepage: https://hackernoon.com/express-fp-an-express-wrapper-for-type-safe-request-handlers-f8c411cc4a7b
- Size: 64.5 KB
- Stars: 64
- Watchers: 4
- Forks: 3
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# express-fp
Type safe request handlers for [Express]. TypeScript compatible.
- Validate Express requests (body and query objects) using [io-ts].
- Construct Express responses without mutation using [express-result-types].
## Example
Below is small example that demonstrates request body and query validation using [io-ts] and fully typed response construction using [express-result-types].
[See the full example](./src/example.ts).
``` ts
const Body = t.interface({
name: t.string,
});
const Query = t.interface({
age: NumberFromString,
});
const requestHandler = wrap(req => {
const jsonBody = req.body.asJson();
const maybeQuery = Query.decode({
age: req.query.get('age').toNullable(),
}).mapLeft(formatValidationErrors('query'));
const maybeBody = jsonBody.chain(jsValue =>
jsValue.validate(Body).mapLeft(formatValidationErrors('body')),
);
return maybeQuery
.chain(query => maybeBody.map(body => ({ query, body })))
.map(({ query, body }) =>
Ok.apply(
new JsValue({
// We defined the shape of the request body and the request query parameter
// 'age' for validation purposes, but it also gives us static types! For
// example, here the type checker knows the types:
// - `body.name` is type `string`
// - `age` is type `number`
name: body.name,
age: query.age,
}),
jsValueWriteable,
),
)
.getOrElseL(error => BadRequest.apply(new JsValue(error), jsValueWriteable));
});
app.post('/', requestHandler);
// ❯ curl --request POST --silent --header 'Content-Type: application/json' \
// --data '{ "name": "bob" }' "localhost:8080/" | jq '.'
// "Validation errors for query: Expecting NumberFromString at age but instead got: null."
// ❯ curl --request POST --silent --header 'Content-Type: application/json' \
// --data '{ "name": "bob" }' "localhost:8080/?age=foo" | jq '.'
// "Validation errors for query: Expecting NumberFromString at age but instead got: \"foo\"."
// ❯ curl --request POST --silent --header 'Content-Type: invalid' \
// --data '{ "name": "bob" }' "localhost:8080/?age=5" | jq '.'
// "Expecting request header 'Content-Type' to equal 'application/json', but instead got 'invalid'."
// ❯ curl --request POST --silent --header 'Content-Type: application/json' \
// --data 'invalid' "localhost:8080/?age=5" | jq '.'
// "JSON parsing error: Unexpected token i in JSON at position 0"
// ❯ curl --request POST --silent --header 'Content-Type: application/json' \
// --data '{ "name": 1 }' "localhost:8080/?age=5" | jq '.'
// "Validation errors for body: Expecting string at name but instead got: 1."
// ❯ curl --request POST --silent --header 'Content-Type: application/json' \
// --data '{ "name": "bob" }' "localhost:8080/?age=5" | jq '.'
// {
// "name": "bob",
// "age": 5
// }
```
## Installation
```
yarn add express-fp
```
## Development
```
yarn
npm run compile
npm run lint
```
[io-ts]: https://github.com/gcanti/io-ts
[fp-ts]: https://github.com/gcanti/fp-ts
[express-result-types]: https://github.com/OliverJAsh/express-result-types
[Express]: https://expressjs.com/