Understanding for Loops

17 June 2020 — Written by Boahs

Understanding for loops

for (let i=0; i<5;i++){
    console.log(`I'm looping!`, i);
}

Above we have one of five types of loops in javascript, and It'll repeat the code inside the block exactly five times. Let's see how it's working exactly.

for (let [initialExpression]; [condition]; [incrementExpression]){
    [statement]
}

The initializing expression is declared
The condition is evaluated, and if it returns true the initial statement will execute. If false the loop will terminate
The statement executes! To execute multiple statements, we use a block statement {...} to group these statments
If the update expression is present the [incrementExpression] is executed.

Are you wondering what the [incrementExpression] did? In javascript adding '++' behind our variable we declared 'i' will add one to it. So having i++ it's incrementing our variable i by one until it's completed that task five times.

Alright let's return back to the previous example:

for (let i=0; i<5;i++){
    console.log(`I'm looping!`, i);
}

We declared our initial expression to start at 0. It'll check that i is less than 5, and if this is true the loop will increment i by one each pass through our loop. Our loop has logic, and knows when to complete!