Splitting an array into 3 unequal arrays in JavaScript

Question

Suppose I have an array of

[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15]

And I want to split it in 3, with two arrays containing the first and last X elements of the original array, and the third array containing the remaining elements, like so:

#1 - [0, 1, 2]
#2 - [3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
#3 - [13, 14, 15]

Is there a shorter/better way of doing that instead of:

const splitBy = 3;
const originalArray = Array.from(Array(16).keys());
const result = [
  originalArray.slice(0, splitBy),
  originalArray.slice(splitBy, -splitBy),
  originalArray.slice(-splitBy),
];

console.log(result)

if it is always split into 3 arrays then this is fine i guess — cmgchess
– cmgchess, Commented Nov 12, 2022 at 13:25
There's no need to make a copy of the array and use it. slice returns a new array of elements each time. — Andy
– Andy, Commented Nov 12, 2022 at 13:42

gog · Accepted Answer · 2022-11-12 13:47:52Z

1

"better" is subjective... however, if you need this more than once, a generic function could be an option:

function multiSlice(a, ...slices) {
    let res = [], i = 0

    for (let s of slices) {
        res.push(a.slice(i, s))
        i = s
    }

    res.push(a.slice(i))
    return res
}

// for example,

const originalArray = Array.from(Array(16).keys());

console.log(multiSlice(originalArray, 3, -3))
console.log(multiSlice(originalArray, 2, 5, 10, 12))

answered Nov 12, 2022 at 13:47

gog

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