ReduceAsync

Asynchronous Array.reduce. The reduce() method applies a function against an accumulator and each value of the array (from left-to-right) to reduce it to a single value.

Installation

$ npm install reduce-async

Syntax

reduceAsync(array, iteratee, done[, initialValue])

Parameters

• array Array - The array to reduce.

• iteratee Function - The function to execute on each value in the array, taking five arguments:

  • prev Any - The value previously returned in the last invocation of the iteratee, or initialValue if supplied.

  • curr Any - The current element being processed in the array.

  • n Integer - The index of the current element being processed in the array. Start at index 0, if an initialValue is provided, and at index 1 otherwise.

  • arr Array - The array reduceAsync was called upon.

  • next Function - The function to call when you are ready to advance to the next element in the array.

• done Function - The function called when the reduce has finished, taking one argument:

  • result Any - The value that results from the reduction.

• initialValue Any (Optional) - Value to use as the first argument to the first call of the iteratee.

More information on how reduce works.

Examples

• Asynchronously sum all the values of an array.

  reduceAsync([0, 1, 2, 3], (prev, curr, n, arr, next) => {
    doSomethingAsync(() => {
      next(prev + curr);
    });
  }, result => {
    // result == 6
  }));

• Asynchronously flatten an array of arrays,

  reduceAsync([[0, 1], [2, 3], [4, 5]], (prev, curr, n, arr, next) => {
    doSomethingAsync(() => {
      next(prev.concat(curr));
    });
  }, result => {
    // result is [0, 1, 2, 3, 4, 5]
  }));

• Asynchronously concatenate all words within an array together starting from an initial value of "foo".

  reduceAsync(['bar', 'baz']], (prev, curr, n, arr, next) => {
    doSomethingAsync(() => {
      next(prev + curr);
    });
  }, result => {
    // result is "foobarbaz"
  }, 'foo'));

Authors

• Nathan Buchar

License

ISC