High Order Functions - Array.prototype.filter

index.js

/**
 * https://jsfiddle.net/ronapelbaum/qk6mcrae/
 */
// HOF get a func and returns a func
function createFilterFunc(fn) {	
	return function(arr) {
  	const res = [];
    for(let i = 0; i < arr.length; i++) {
    	if(!!fn(arr[i])) {
        res.push(arr[i]);
      }
    }
    return res;
  }
}

// ====================
const arr = [1, 3, 5, 4, 8];

const isEven = d => d%2 === 0;
const filterEven = createFilterFunc(isEven);

console.log('even array.filter', arr.filter(isEven));
console.log('even filterEven', filterEven(arr));