tswrap
v1.0.4
Published
Random assortment of Typescript utilities, wrappers, and types.
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tswrap
Random assortment of Typescript utilities, wrappers, and types.
Premise
Ditch the required usage of try
/catch
for async
/await
functions.
Return errors normally, utilise typescript types to force errors to be handled.
Usage
Install it: npm install tswrap --save
Require it: import * as tswrap from 'tswrap'
API
tswrap.R<ReturnType>
Shorthand for Promise<NodeJS.ErrnoException | T>
Where T
is a possible return type.
Best paired with an async function.
async function getItemById (id: string): tswrap.R<Item> {
return database.lookup(id)
}
Functions marked with this return type always may return an error, and should be handled accordingly.
tswrap.RE
A utility function to mark that a function returns a promise that may return an error, but no other values you care about.
Equivalent to tswrap.R<null>
.
tswrap.isError(value)
This function is used to check if the value returned from a function that has the return type of tswrap.R
is an actual error.
If this function returns true
, typescript knows the value is of type tswrap.E
.
If false
, typescript knows the value is of the type T
that was passed into tswrap.R<T>
.
async function setPlayerConfirmedStatus (status: boolean): tswrap.R<Player> {
...
}
const playerUpdateResult = await setPlayerConfirmedStatus(true)
// playerUpdateResult type here is `tswrap.E | Player`
// Trying to access the variable as a `Player` will result in an error.
if (tswrap.isError(playerUpdateResult)) {
// We have now narrowed the type of playerUpdateResult
// to `tswrap.E`, and can handle that appropriately.
console.error(`Error updating player: ${playerUpdateResult}`)
return playerUpdateResult
}
// As long as we `return` from inside `isError`, typescript
// now knows that playerUpdateResult can no longer be `tswrap.E`,
// and as such, narrows the type back to `Player`.
console.log('Player email:', player.email)
tswrap.wrapPromise<ReturnType>(promise)
This function is used to wrap external promises that do not conform to the tswrap.R
return type.
function updatePlayerEmail (id: string, email: string): Promise<Player> {
return new Promise((resolve, reject) => {
database.updatePlayer({ id }, { email }, (err, player) => {
if (err) return reject(err)
return resolve(player)
})
})
}
const playerUpdateResult = await tswrap.wrapPromise<Player>(updatePlayerEmail(id, player))
if (tswrap.isError(playerUpdateResult)) {
...
}
tswrap.wrapAxios<ReturnType>(promise)
Higher level wrapper for axios results.
Will return either an AxiosError
, or an AxiosResponse<ReturnType>
value.
See tswrap.isAxiosError
for an example.
tswrap.isAxiosError(value)
Used to check if the response from tswrap.wrapAxios
is an AxiosError
.
interface Response { id: string }
const result = await tswrap.wrapAxios<Response>(axios.get('https://my.com/api'))
if (tswrap.isAxiosError(result)) {
return result
}
// result.data is now typed to the parameter passed to `tswrap.wrapAxios`
console.log('Got ID:', result.data.id)
tswrap.parseData<ReturnType>(data, structure)
Used in conjunction with io-ts for doing runtime validation.
Wraps structure.decode()
into a tswrap compliant function.
See tswrap.isParseError
for an example.
tswrap.isParseError(value)
Used to check if the response from tswrap.parseData
is an error.
const requestSchema = iots.interface({ id: iots.string })
type RequestSchemaType = iots.TypeOf<typeof requestSchema>
const request = { id: 123 }
const parsedData = tswrap.parseData<RequestSchemaType>(request, requestSchema)
if (tswrap.isParseError(parsedData)) {
// parsedData here is the raw Left<iots.Errors, any>
// allowing you to use your own reporters to return an error
return parsedData
}
console.log('Got ID:', parsedData.id)