duck-fp

Task Either

TaskEither represents computation that might fail.

tryCatch()

• Function signature

  <T, E>(
    tryFn: () => Promise<T>,
    catchFn: (e: unknown) => E,
  ): TaskEither<E, T>
  

• tryFn a function that may throw an Error
• catchFn a function that is called when tryFn throwed something
• returns TaskEither containing either right containg the result of tryFn or if tryFn throws an Error left containing the result of catchFn
• Code example

  import { toError } from "@victorenokh/maybe.ts/either"
  import { tryCatch } from "@victorenokh/maybe.ts/task-either"
  
  const parseOrThrow = (res: Response) => {
    if (!res.ok) {
      throw new Error(res.statusText)
    }
  
    return res.text()
  }
  
  const fetchString = (url: string) =>
    tryCatch(() => fetch(url).then(parseOrThrow), toError)
  
  fetchString('https://example.com').fold(
    console.error,
    console.log,
  ) // Output: html string of example.com site
  fetchString('https://example.com/non/existing/path').fold(
    console.error,
    console.log,
  ) // Ouput: Error: internal server error
  

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