JavaScript: Apply a function against an accumulator and each element in the array (from left to right), returning an array of successively reduced values

JavaScript: Exercise-156 with Solution

Array Successive Reduce Values

Write a JavaScript program to apply a function against an accumulator and each element in the array (from left to right), returning an array of successively reduced values.

• Use Array.prototype.reduce() to apply the given function to the given array, storing each new result.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
// Define a function 'reduceSuccessive' that applies a binary function to the elements of an array
// Successively reduce the array using the provided binary function and an initial accumulator value
const reduceSuccessive = (arr, fn, acc) =>
  // Use the 'reduce' method on the array
  arr.reduce(
    // For each element of the array, push the result of applying the binary function to the accumulator and the current value
    // into the result array
    (res, val, i, arr) => (res.push(fn(res.slice(-1)[0], val, i, arr)), res),
    // Initialize the result array with the provided accumulator value
    [acc]
  );

// Test the 'reduceSuccessive' function with an array, a binary function, and an initial accumulator value
console.log(reduceSuccessive([1, 2, 3, 4, 5, 6], (acc, val) => acc + val, 0)); // Output: [0, 1, 3, 6, 10, 15, 21]

Output:

[0,1,3,6,10,15,21]

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-156-1 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that applies a reducer function to an array and returns an array of all intermediate accumulator values.
• Write a JavaScript function that mimics the behavior of scan (cumulative reduce) and outputs each step’s result.
• Write a JavaScript program that, given an array and a binary function, produces an array of partial sums using reduce.
• Write a JavaScript program that creates a successive reduction array for a list of numbers with a custom combining function.

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