Split an Array with specific chunks size

Question

For example I have a chunks array, this array has the sizes of individual chunks.

let example = [3,3]; // Chunks array
let auxarrayindex = [1,2,3,4,5,6]; // Array that I want to splice
let example2 = [3,2,3]; // Chunks array
let auxarrayindex2 = [1,2,3,4,5,6,7,8]; // Array that I want to splice

The result that I want is:

[1,2,3],[4,5,6] and the second [1,2,3],[4,5],[6,7,8]

This is my code:

for (let auxexample = 0; auxexample < example.length; auxexample++) {
    finalauxarray.push(auxarrayindex.slice(0, example[auxexample]));
}

The result from my code is:

[1,2,3],[1,2,3] and the second [1,2,3],[1,2],[1,2,3]

trincot · Accepted Answer · 2020-06-22 20:39:47Z

6

The problem is that your slice always starts at the same index (0).

Use a variable (like i) that you increase as you take chunks:

let example = [3,2,3];
let auxarrayindex = [1,2,3,4,5,6,7,8];

let finalauxarray = [];
let i = 0;
for (let auxexample = 0; auxexample < example.length; auxexample++) {
   finalauxarray.push(auxarrayindex.slice(i, i+=example[auxexample]));
}

console.log(finalauxarray);

You could also use map for your loop:

let example = [3,2,3];
let auxarrayindex = [1,2,3,4,5,6,7,8];

let i = 0;
let finalauxarray = example.map(size => auxarrayindex.slice(i, i+=size));

console.log(finalauxarray);

edited Jun 22, 2020 at 20:39

answered Jun 22, 2020 at 20:34

trincot

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1 Comment

Xavier Duvan Melo Over a year ago

Thanks!! a simple method

Kirmin · Accepted Answer · 2020-06-22 20:42:47Z

3

The problem is because of the slice parameters are wrong You can learn more about how slice works on this link

https://www.w3schools.com/jsref/jsref_slice_array.asp

It takes as first parameter the starti g position and as last parameter the ending position which is not included in the result

You can aslo use splice for this as well https://www.w3schools.com/jsref/jsref_splice.asp

Hope that helps

answered Jun 22, 2020 at 20:42

Kirmin

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Comments

pretzelhammer · Accepted Answer · 2020-06-22 20:44:04Z

2

Working example using splice instead of slice as I think it offers a slightly cleaner API for this particular use-case:

let example = [3, 3];
let auxArrayIndex = [1, 2, 3, 4, 5, 6];
let example2 = [3, 2, 3];
let auxArrayIndex2 = [1, 2, 3, 4, 5, 6, 7, 8];

function getChunks(chunkSizes, array) {
  let result = [];
  for (let chunkSize of chunkSizes) {
    result.push(array.splice(0, chunkSize));
  }
  return result;
}

let chunks = getChunks(example, auxArrayIndex);
let chunks2 = getChunks(example2, auxArrayIndex2);

console.log(chunks); // logs "[1,2,3], [4,5,6]"
console.log(chunks2); // logs "[1,2,3], [4,5], [6,7,8]"

edited Jun 22, 2020 at 20:44

answered Jun 22, 2020 at 20:35

pretzelhammer

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