Order of code in while loop

JavaScript
#1

Hi

Can someone clarify for me please why in the following code the i increment function come after the push the code to push the value of i?

   var myArray = [];
   var i = 0;
   while( i <= 5 && i >= 0) {
       myArray.push(i);
       i--  ;   
}

The purpose of the code is to take i and take one off each time for 5 consecutive times and add each value to the array.

Another question I have is using for in the loop.

var myArray = [];

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

The above works but why doesn’t it work as the previous piece of code and setting i to 0 if it is being incremented by one THEN added to the array.

The code is suppossed take i and add one each time until 5 s reached and adding each value on the way from 1 to 5 into the array.

But i =1

after the first loop runs it will be 2 thats added no?

Could

**Your code so far**


// Setup
var myArray = [];
var i = 0
while(i <= 5 && i >= 0){
myArray.push(i)
i--
}

// Only change code below this line

**Your browser information:**

User Agent is: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/88.0.4324.182 Safari/537.36 Edg/88.0.705.74.

Challenge: Iterate with JavaScript While Loops

Link to the challenge:

#2

I’ve edited your post for readability. When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

Pre-formatted-text
Pre-formatted-text1356×380 401 KB

See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (’).

#3

Let’ talk about what the above code is doing. You start with an empty array named myArray. You start with i set to 0. Next, you check the while loop condition. Is i less than or equal to 5 AND i is greater to or equal to 0? The answer is yes, 0 < = 5 AND 0 >= 0, so you then push the value of i (which is currently 0) into myArray. Finally, you decrement i by one using the --i. Now i is -1, so when you check the while loop condition, it no longer evaluates to true because even though - is less than or equal to 5, -1 is not greater than or equal to 0, so the code within the while loop is not processed and the loop ends. The final value of myArray ends up being [0] (an array with one element - the value 0).

#4

In the above code, i starts at 1 and will be incremented by 1 at the end of each iteration of the for loop.

  • In the first iteration, i is 1, so the value 1 gets pushed to myArray. At the end of this iteration, i gets incremented by 1
  • In the next iteration, i is 2, so the value 2 gets pushed to myArray. At the end of this iteration, i gets incremented by 1
  • In the next iteration, i is 3, so the value 3 gets pushed to myArray. At the end of this iteration, i gets incremented by 1
  • In the next iteration, i is 4, so the value 4 gets pushed to myArray. At the end of this iteration, i gets incremented by 1
  • In the next iteration, i is 5, so the value 5 gets pushed to myArray. At the end of this iteration, i gets incremented by 1
  • At this point, i is now 6, so the for loop condition of i <= 5 is no longer true, so the loop ends and the value of myArray is [0, 1, 2, 3, 4, 5]