# freeCodeCamp Challenge Guide: Iterate with JavaScript For Loops

freeCodeCamp Challenge Guide: Iterate with JavaScript For Loops
0

#1

The most common type of JavaScript loop is called a `for loop` because it runs `for` a specific number of times.

``````var ourArray = [];
for(var i = 0; i < 5; i++) {
ourArray.push(i);
}
``````

ourArray will now contain [0,1,2,3,4]

## More about for loops

``````for(var i = 0; i < 5; i++) {  // There are 3 parts here
``````

There are three parts to for loop. They are separated by semicolons.

1. The initialization: `var i = 0;` - This code runs only once at the start of the loop. It’s usually used to declare the counter variable (with `var`) and initialize the counter (in this case it is set to 0).

2. The condition: `i < 5;` - The loop will run as long as this is `true`. That means that as soon as `i` is equal to 5, the loop will stop looping. Note that the inside of the loop will never see `i` as 5 because it will stop before then. If this condition is initially `false`, the loop will never execute.

3. The increment: `i++` - This code is run at the end of each loop. It’s usually a simple increment (`++` operator), but can really be any mathematical transformation. It is used to move the counter (`i`) forward (or backwards, or whatever.

#2

The tricky part of this one for me was the i = 0.
if i =0 then the array starts with 0 and the challenge wants you to start at 1.

So I changed i = 1 and then i < 6 so the result was an array [1, 2, 3, 4, 5]

for (var i = 1; i < 6 ; i++) {

#3

This worked for me

var myArray = [];
for(var i=1; i<=5; i++){
myArray.push(i);
}

#4

I’ve solved the challenge but I don’t understand why I’ve to put myArray.push(i).

What’s the use of push here? I thought push is for us to attend the data to the end of an array but I don’t see how it’s applied here.

#5

You’re totally correct - `.push()` adds the value to the end of the array. In our case, since we have an empty array to begin with, when we push a value, it becomes the only value in the array. However, it’s important to remember that we are always adding values to the end of the array.

So, what our loop

``````var myArray = [];

for (var i = 1; i <= 5; i++) {
myArray.push(i);
}
``````

does is this:

``````myArray = [1],
myArray = [1,2],
myArray = [1,2,3],
myArray = [1,2,3,4],
myArray = [1,2,3,4,5]``````

#6

To push the values 1 through 5,it means start looping at 1 through 5( inclusive).Like this (var a = 1;a <= 5;a++)

// Example
var ourArray = [];

for (var i = 0; i < 5; i++) {
ourArray.push(i);
}

// Setup
var myArray = [];

// Only change code below this line.
for(var a = 1;a <= 5;a++) {
myArray.push(a);
}

#7

Iteration in JavaScript is so great and easy!

My code here:

``````// Setup
var myArray = [];

// Only change code below this line.
for (var kbp = 1; kbp < 6; kbp++) {
myArray.push(kbp);
}``````