Function callbackify

  • Takes an async function (or a function that returns a Promise) and returns a function following the error-first callback style, i.e. taking an (err, value) => ... callback as the last argument. In the callback, the first argument will be the rejection reason (or null if the Promiseresolved), and the second argument will be the resolved value.

    const util = require('util');

    async function fn() {
      return 'hello world';
    }
    const callbackFunction = util.callbackify(fn);

    callbackFunction((err, ret) => {
      if (err) throw err;
      console.log(ret);
    });

    Will print:

    hello world

    The callback is executed asynchronously, and will have a limited stack trace. If the callback throws, the process will emit an 'uncaughtException' event, and if not handled will exit.

    Since null has a special meaning as the first argument to a callback, if a wrapped function rejects a Promise with a falsy value as a reason, the value is wrapped in an Error with the original value stored in a field namedreason.

    function fn() {
      return Promise.reject(null);
    }
    const callbackFunction = util.callbackify(fn);

    callbackFunction((err, ret) => {
      // When the Promise was rejected with `null` it is wrapped with an Error and
      // the original value is stored in `reason`.
      err && Object.hasOwn(err, 'reason') && err.reason === null;  // true
    });

    Returns

    a callback style function

    Parameters

    • fn: (() => Promise<void>)
        • (): Promise<void>

        • Returns Promise<void>

    Returns ((callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • TResult

    Parameters

    • fn: (() => Promise<TResult>)
        • (): Promise<TResult>

        • Returns Promise<TResult>

    Returns ((callback: ((err: ErrnoException, result: TResult) => void)) => void)

  • Type Parameters

    • T1

    Parameters

    • fn: ((arg1: T1) => Promise<void>)
        • (arg1: T1): Promise<void>

        • Parameters

          • arg1: T1

          Returns Promise<void>

    Returns ((arg1: T1, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • TResult

    Parameters

    • fn: ((arg1: T1) => Promise<TResult>)
        • (arg1: T1): Promise<TResult>

        • Parameters

          • arg1: T1

          Returns Promise<TResult>

    Returns ((arg1: T1, callback: ((err: ErrnoException, result: TResult) => void)) => void)

  • Type Parameters

    • T1

    • T2

    Parameters

    • fn: ((arg1: T1, arg2: T2) => Promise<void>)
        • (arg1: T1, arg2: T2): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • T2

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2) => Promise<TResult>)
        • (arg1: T1, arg2: T2): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • T2

    • T3

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • arg4: T4
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException) => void)): void

      • Parameters

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • arg4: T4
        • arg5: T5
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    • T6

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5
          • arg6: T6

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException) => void)): void

      • Parameters

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    • T6

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5
          • arg6: T6

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • arg4: T4
        • arg5: T5
        • arg6: T6
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Takes an async function (or a function that returns a Promise) and returns a function following the error-first callback style, i.e. taking an (err, value) => ... callback as the last argument. In the callback, the first argument will be the rejection reason (or null if the Promiseresolved), and the second argument will be the resolved value.

    const util = require('util');

    async function fn() {
      return 'hello world';
    }
    const callbackFunction = util.callbackify(fn);

    callbackFunction((err, ret) => {
      if (err) throw err;
      console.log(ret);
    });

    Will print:

    hello world

    The callback is executed asynchronously, and will have a limited stack trace. If the callback throws, the process will emit an 'uncaughtException' event, and if not handled will exit.

    Since null has a special meaning as the first argument to a callback, if a wrapped function rejects a Promise with a falsy value as a reason, the value is wrapped in an Error with the original value stored in a field namedreason.

    function fn() {
      return Promise.reject(null);
    }
    const callbackFunction = util.callbackify(fn);

    callbackFunction((err, ret) => {
      // When the Promise was rejected with `null` it is wrapped with an Error and
      // the original value is stored in `reason`.
      err &#x26;&#x26; Object.hasOwn(err, 'reason') &#x26;&#x26; err.reason === null;  // true
    });

    Returns

    a callback style function

    Parameters

    • fn: (() => Promise<void>)
        • (): Promise<void>

        • Returns Promise<void>

    Returns ((callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • TResult

    Parameters

    • fn: (() => Promise<TResult>)
        • (): Promise<TResult>

        • Returns Promise<TResult>

    Returns ((callback: ((err: ErrnoException, result: TResult) => void)) => void)

  • Type Parameters

    • T1

    Parameters

    • fn: ((arg1: T1) => Promise<void>)
        • (arg1: T1): Promise<void>

        • Parameters

          • arg1: T1

          Returns Promise<void>

    Returns ((arg1: T1, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • TResult

    Parameters

    • fn: ((arg1: T1) => Promise<TResult>)
        • (arg1: T1): Promise<TResult>

        • Parameters

          • arg1: T1

          Returns Promise<TResult>

    Returns ((arg1: T1, callback: ((err: ErrnoException, result: TResult) => void)) => void)

  • Type Parameters

    • T1

    • T2

    Parameters

    • fn: ((arg1: T1, arg2: T2) => Promise<void>)
        • (arg1: T1, arg2: T2): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • T2

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2) => Promise<TResult>)
        • (arg1: T1, arg2: T2): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • T2

    • T3

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, callback: ((err: ErrnoException) => void)) => void)

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • arg4: T4
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException) => void)): void

      • Parameters

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • arg4: T4
        • arg5: T5
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    • T6

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6) => Promise<void>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6): Promise<void>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5
          • arg6: T6

          Returns Promise<void>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException) => void)): void

      • Parameters

        Returns void

  • Type Parameters

    • T1

    • T2

    • T3

    • T4

    • T5

    • T6

    • TResult

    Parameters

    • fn: ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6) => Promise<TResult>)
        • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6): Promise<TResult>

        • Parameters

          • arg1: T1
          • arg2: T2
          • arg3: T3
          • arg4: T4
          • arg5: T5
          • arg6: T6

          Returns Promise<TResult>

    Returns ((arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException | null, result: TResult) => void)) => void)

      • (arg1: T1, arg2: T2, arg3: T3, arg4: T4, arg5: T5, arg6: T6, callback: ((err: ErrnoException | null, result: TResult) => void)): void

      • Parameters

        • arg1: T1
        • arg2: T2
        • arg3: T3
        • arg4: T4
        • arg5: T5
        • arg6: T6
        • callback: ((err: ErrnoException | null, result: TResult) => void)

        Returns void

Settings

Member Visibility

Theme

Generated using TypeDoc