I have a Javascript array that I would like to split into two based on whether a function called on each element returns true or false. Essentially
I came up with this little guy. It uses for each and all that like you described, but it looks clean and succinct in my opinion.
//Partition function
function partition(array, filter) {
let pass = [], fail = [];
array.forEach((e, idx, arr) => (filter(e, idx, arr) ? pass : fail).push(e));
return [pass, fail];
}
//Run it with some dummy data and filter
const [lessThan5, greaterThanEqual5] = partition([0,1,4,3,5,7,9,2,4,6,8,9,0,1,2,4,6], e => e < 5);
//Output
console.log(lessThan5);
console.log(greaterThanEqual5);