for

The for statement creates a loop that consists of three expressions separated by semi-colons and enclosed in parentheses. The three expressions are as follows:

1. The initialization of the iterator
2. The condition to check before each loop to see if the loop should continue
3. The iteration of the iterator

for (initialization; condition; iteration) {...}

The body of the for statement is enclosed in a set of curly braces ({}) and is executed each the statement loops as long as the condition evaluates to true.

for (let i = 0; i < 5; i++) {
  console.log(i) // 0 1 2 3 4
}

let total = 0

for (let i = 0; i < 5; i++) {
  total += i
}

console.log(total) // 10

The for statement can also be used to iterate over arrays by using the iterator as the array index.

const animals = ['cat', 'dog', 'mouse']

for (let i = 0; i < animals.length; i++) {
  // Logs all the animals in the array
  console.log(animals[i]) 
}

const numbers = [10, 20, 30, 40, 50, 60, 70, 80, 90];
let total = 0

for (let i = 0; i < numbers.length; i++) {
  total += numbers[i]  
}

console.log(total) // 450

This YouTube video was created by Steve Griffith.