Documentation

Student-friendly HTML, CSS, and JavaScript reference with examples

Sections


                                        for...of


                                        accumulator


                                        for (i...)


                                        nested loops

Traditional For Loop (for-i)

A traditional for loop gives you both the index (position) and the value.

for (let i = 0; i < array.length; i++) {
  // code runs for each index
}

Three Parts

let i = 0 - start counter at 0
i < array.length - continue while i is less than array length
i++ - add 1 to i after each iteration

Accessing Elements by Index

const numbers = [10, 20, 30];
for (let i = 0; i < numbers.length; i++) {
  console.log(i, numbers[i]);
}
// Prints:
// 0 10
// 1 20
// 2 30

When to Use For-i

Use for-i when you need:

The index (position)
To compare value with its position
To access elements by index

The Index Variable

The variable i IS the index itself:

if (array[i] > i) {
  // element is greater than its position
}