Summary  
This chapter demonstrates how to use loops—particularly for loops—to iterate through arrays by index using the length property, enabling printing each element and performing bulk updates on array values.

General domain of usage  
Data processing

Loops enable us to efficiently go through all or specific elements of an array.

For example, we can use a for loop to iterate through all elements of an array and output them:

let numbers = [1, 1, 2, 3, 5, 8, 13, 21];

for(let i = 0; i < numbers.length; i++) {
  console.log("Element " + (i + 1) + " of the array is: " + numbers[i]);
}

This is especially useful when we need to perform an operation on multiple elements in an array:

let numbers = [1, 1, 2, 3, 5, 8, 13, 21];

console.log("Before:", numbers);
for(let i = 0; i < numbers.length; i++) {
  numbers[i] *= 2;
}
console.log("After:", numbers);

We can use a `while` or a `do-while` loop for this purpose as well, however, that is not the convention. 

let numbers = [1, 1, 2, 3, 5, 8, 13, 21];

console.log("Before:", numbers);
let i = 0;
while(i < numbers.length) {
  numbers[i] *= 2;
  i += 1;
}
console.log("After:", numbers);

Even though the same results can be achieved using `while` or `do-while` loops, it is recommended to use a `for` loop when iterating through arrays because it is the conventional and more readable approach.

Does the following code modify the original array?

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Using Loops with Arrays

1. What does the following code output?

2. Does the following code modify the original array?

Using Loops with Arrays

1. What does the following code output?

2. Does the following code modify the original array?