Split an Array based on callback

partition.js

Array.prototype.partition = function(predicate) {

	const results = [[], []];
  
  
  this.forEach((item, index) => {
    
  		results[predicate(item, index) ? 0 : 1].push(item);
    
  });
  
  
	return results;
};

const [evens, odds] = [1, 2, 3, 4, 5].partition(n => n % 2 == 0);

console.log(evens); // [2, 4]
console.log(odds);	// [1, 3, 5]