JavaScript: Combine the numbers of a given array into an array containing all combinations

JavaScript fundamental (ES6 Syntax): Exercise-9 with Solution

All Combinations from Array of Numbers

Write a JavaScript program to combine the numbers of a given array into an array containing all combinations.

• Use Array.prototype.reduce() combined with Array.prototype.map() to iterate over elements and combine into an array containing all combinations.

Sample Solution:

JavaScript Code:

//#Source https://bit.ly/2neWfJ2 
// Define a function called `powerset` that takes an array `arr`.
const powerset = arr => 
  // Reduce the array to generate the powerset.
  arr.reduce(
    // For each element in the array, concatenate it with each element of the accumulated result.
    (a, v) => a.concat(a.map(r => [v].concat(r))), 
    [[]]
  );

// Test cases
console.log(powerset([1, 2]));  
console.log(powerset([1, 2, 3]));  
console.log(powerset([1, 2, 3, 4]));

Output:

[[],[1],[2],[2,1]]
[[],[1],[2],[2,1],[3],[3,1],[3,2],[3,2,1]]
[[],[1],[2],[2,1],[3],[3,1],[3,2],[3,2,1],[4],[4,1],[4,2],[4,2,1],[4,3],[4,3,1],[4,3,2],[4,3,2,1]]

Visual Presentation:

Flowchart:

Live Demo:

See the Pen javascript-basic-exercise-1-9 by w3resource (@w3resource) on CodePen.

For more Practice: Solve these Related Problems:

• Write a JavaScript program that generates all possible pair combinations from an array of numbers.
• Write a JavaScript function that returns every possible subset combination of numbers from a given array.
• Write a JavaScript program that creates an array of all possible combinations (of any length) from an input array of numbers.

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