I'd like to transform an array like the following:
const myArray = [ 'a', 'b', 'c', 'd', 'e', 'f' ];
to something like this:
const transformedArray = [ [ 'a', 'b' ], [ 'c', 'd' ], [ 'e', 'f' ] ];
The only way I see is to do it with a good old for loop, but is there a more elegant way to do it with Array.prototype functions ?
You could do something like this using reduce, Math.floor and %
const myArray = ['a', 'b', 'c', 'd', 'e', 'f']
const newArray = myArray.reduce((acc, a, i) => {
const index = Math.floor(i/2);
acc[index] = acc[index] || [];
acc[index][i % 2] = a
return acc
}, [])
console.log(newArray)Math.floor(i/2) gets which of the inner array the item belongs toi % 2 gets which postion of the inner array the item belongs toYou can use Array.from() to create an array of chunks:
const myArray = [ 'a', 'b', 'c', 'd', 'e', 'f', 'g' ];
const chunk = n => arr =>
Array.from({ length: Math.ceil(arr.length / n) }, (_, i) =>
myArray.slice(i * n, (i + 1) * n)
);
const log = arr => console.log(JSON.stringify(arr));
log(chunk(2)(myArray)); // [["a","b"],["c","d"],["e","f"],["g"]]
log(chunk(3)(myArray)); // [["a","b","c"],["d","e","f"],["g"]]The solution below uses reduce to iterate over the items in the array. We use a modulo check on the index of the item to determine whether or not we need to start a new array.
The code adds in an object when it's inspecting an index which doesn't need to be formed into a new array. We later filter these objects out. There may be a more elegant way of doing this, but I feel it works out quite nicely.
const letters = [ 'a', 'b', 'c', 'd', 'e', 'f' ];
const splitIntoChunks = (arrayIn, size) => arrayIn.reduce(
(prev, curr, i) => [
...prev,
i % size === 0
? arrayIn.slice(i, i + size)
: { '__remove': true }
],
[],
).filter(x => !x['__remove'])
const result = splitIntoChunks(letters, 2)
console.dir(result)One other solution that has been given to me which I find the most readable.
const myArray = [ 'a', 'b', 'c', 'd', 'e', 'f' ];
const transformedArray = Array(myArray.length / 2).fill().map((_, i) => [myArray[i * 2], myArray[i * 2 + 1]]);
console.log(transformedArray);