[ruslan_mart]

const filterByA = arr => {
    const res = [];

    for(let item of arr) {
        if(item != null && item.toString().charAt(0) === 'A') {
              res.push(item);
        }
    }

    return res;
}

console.log( filterByA(['Apple', 'Banana', 'Orange', 'Avocado', 'Cheese']) );

const arrayStartsWith = by => arr => {
	const res = [];

	for(let item of arr) {
		if(item != null && item.toString().charAt(0) === by) {
			res.push(item);
		}
	}

	return res;
};


const filterByA = arrayStartsWith('A');
const filterByB = arrayStartsWith('B');

let testArr = ['Apple', 'Banana', 'Orange', 'Avocado', 'Cheese', 'Black Chocolate'];


console.log( filterByA(testArr) );
console.log( filterByB(testArr) );