let index = 0;
const array = [1,2,3,4,5,6];

while (index < array.length) {
  console.log(array[index]);
  index++;
}


// ****** //
const array = [1,2,3,4,5,6];
for (let index = 0; index < array.length; index++) {
  console.log(array[index]);
}


// ****** //
const array = [1,2,3,4,5,6];

array.forEach(function(current_value, index, array) {
  console.log(`At index ${index} in array ${array} the value is ${current_value}`);
});
// => undefined
map

// ****** //

const array = [1,2,3,4,5,6];
const square = x => Math.pow(x, 2);
const squares = array.map(square);
console.log(`Original array: ${array}`);
console.log(`Squared array: ${squares}`);

// ****** //

reduce

const array = [1,2,3,4,5,6];
const sum = (x, y) => x + y;
const array_sum = array.reduce(sum, 0);
console.log(`The sum of array: ${array} is ${array_sum}`);

// ****** //
filter

const array = [1,2,3,4,5,6];
const even = x => x % 2 === 0;
const even_array = array.filter(even);
console.log(`Even numbers in array ${array}: ${even_array}`);

// ****** //

const array = [1,2,3,4,5,6];
const under_seven = x => x < 7;

if (array.every(under_seven)) {
  console.log('Every element in the array is less than 7');
} else {
  console.log('At least one element in the array was bigger than 7');
}


some // ****** //

const array = [1,2,3,9,5,6,4];
const over_seven = x => x > 7;
if (array.some(over_seven)) {
  console.log('At least one element bigger than 7 was found');
} else {
  console.log('No element bigger than 7 was found');
}