slices an array based either on the condition of an element, or just uniformly by quantity

sliceArrayOnCondition.js

const sliceArrayOnCondition=(a,f)=>a.reduce((x,v,i)=>((isNaN(f)?f(v):i%f===0)&&i!==0?x.push([v]):x.at(-1).push(v),x),[[]]);

this takes two arguments: first, the array to slice up; then either a function to use for testing the element or just a number that the array will be evenly divided into groups of

so, to split up an array called 'arr' into equal groups of three-elements, you would do this:
sliceArrayOnCondition(arr, 3)

if you want to split it up on every element that is a string, you would do:
sliceArrayOnCondition(arr, v => typeof v === 'string')

or maybe you want to split it up on everything that is an html DOM object:
sliceArrayOnCondition(arr, v => v instanceof Element)