What is the best way to iterate through arrays in javascript?

Question

What is the best way to iterate through arrays in javascript?

Could someone please assist me with looping through an array of variable sizes? Here is the array:

var x = [[1,2,3],[8],[10,11,12],[13]];

I am trying to create combinations in a new array. For example:

y = [[1,8,10,13],[2,8,10,13],[3,8,10,13],
[1,8,11,13],[2,8,11,13],[3,8,11,13]....]

I hope this explanation is clear. Here is what I have attempted so far:

for(var i=0; i<x.length; i++)
{
    for(var ii=0; x[i].length; ii++)
    {
        //At this point I have x[0], but each number needs to be part of a combination 
    }
}

My end goal is to create combinations across multiple lists, such as the one below with 4 lists:

javascript arrays indexing

Answer 1

Answer №1

This resembles the concept of a cartesian product and recursion with a single for loop can be utilized to achieve this.

var array = [[1,2,3],[8],[10,11,12],[13]];

function generateCartesianProduct(data) {
  var result = [];

  function compute(data, n, c) {
    if (n == data.length) {
      result.push(c.slice())
      return;
    }

    for (var i = 0; i < data[n].length; i++) {
      c[n] = data[n][i];
      compute(data, n + 1, c);
    }
  }

  compute(data, 0, [])
  return result
}

console.log(JSON.stringify(generateCartesianProduct(array)))

Answer 2

This resembles the concept of a cartesian product and recursion with a single for loop can be utilized to achieve this.

var array = [[1,2,3],[8],[10,11,12],[13]];

function generateCartesianProduct(data) {
  var result = [];

  function compute(data, n, c) {
    if (n == data.length) {
      result.push(c.slice())
      return;
    }

    for (var i = 0; i < data[n].length; i++) {
      c[n] = data[n][i];
      compute(data, n + 1, c);
    }
  }

  compute(data, 0, [])
  return result
}

console.log(JSON.stringify(generateCartesianProduct(array)))

Answer 3

Answer №2

function generateCombinations(arr, currentIndex, currentCombo) {

    if (currentIndex == arr.length) {
        console.log(currentCombo);
        return;
    }

    for (var j = 0; j < arr[currentIndex].length ; ++j) {
        currentCombo.push(arr[currentIndex][j]);
        generateCombinations(arr, currentIndex+1, currentCombo);
        currentCombo.pop();
    }
}

generateCombinations([[1,2,3],[8],[10,11,12],[13]], 0, []);

Output :

[ 1, 8, 10, 13 ]
[ 1, 8, 11, 13 ]
[ 1, 8, 12, 13 ]
[ 2, 8, 10, 13 ]
[ 2, 8, 11, 13 ]
[ 2, 8, 12, 13 ]
[ 3, 8, 10, 13 ]
[ 3, 8, 11, 13 ]
[ 3, 8, 12, 13 ]

Answer 4

function generateCombinations(arr, currentIndex, currentCombo) {

    if (currentIndex == arr.length) {
        console.log(currentCombo);
        return;
    }

    for (var j = 0; j < arr[currentIndex].length ; ++j) {
        currentCombo.push(arr[currentIndex][j]);
        generateCombinations(arr, currentIndex+1, currentCombo);
        currentCombo.pop();
    }
}

generateCombinations([[1,2,3],[8],[10,11,12],[13]], 0, []);

Output :

[ 1, 8, 10, 13 ]
[ 1, 8, 11, 13 ]
[ 1, 8, 12, 13 ]
[ 2, 8, 10, 13 ]
[ 2, 8, 11, 13 ]
[ 2, 8, 12, 13 ]
[ 3, 8, 10, 13 ]
[ 3, 8, 11, 13 ]
[ 3, 8, 12, 13 ]

What is the best way to iterate through arrays in javascript?

Answer №1

Answer №2

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