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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Iterating through an Array

Micah Dunson
Micah Dunson
34,368 Points
Posted by Micah Dunson
Micah Dunson
34,368 Points

Need Help with Arrays

I need to create a FOR or WHILE loop to run thru the following:

​var temperatures = [100,90,99,80,70,65,30,10];

This is my FOR loop, however it is incorrect and I don't know what I'm doing wrong:

for ( var i = 0, i > temperatures.length; i += 1 ) { console.log(temperatures[i]); }

script.js 
​var temperatures = [100,90,99,80,70,65,30,10];
for ( var i = 0, i > temperatures.length; i += 1 ) {
  console.log(temperatures[i]);
}
index.html 
<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <title>JavaScript Loops</title>
</head>
<body>
<script src="script.js"></script>
</body>
</html>

3 Answers

Marcus Parsons
Marcus Parsons
15,719 Points

Hi Micah,

Your error is that you have a comma inside of your for loop right after creating the variable i and this should be a semicolon. Also, you need to use the < and not > because i is starting at 0 and 0 can't be greater than the length of the array meaning that your for loop would never execute.

var temperatures = [100,90,99,80,70,65,30,10];
//change comma to a semicolon
//also change > to <
for ( var i = 0; i < temperatures.length; i += 1 ) {
  console.log(temperatures[i]);
}
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

Wow... guess it's time to call it a night. LOL... I didn't catch that... and realize now that i+=1 IS right (just a different way of i++) ... haha.

Need to limit the amount of hours I stare at the computer screen, apparently! :/ Thanks Marcus.

Marcus Parsons
Marcus Parsons
15,719 Points

Jason, you're trying buddy, and that's what counts! Keep on helping out and being an awesome student! :)

Micah Dunson
Micah Dunson
34,368 Points
Micah Dunson
Micah Dunson
34,368 Points

Thank you I appreciate it. It's always the little thing lol

Marcus Parsons
Marcus Parsons
15,719 Points

You're very welcome, Micah! I know what you mean haha Happy Coding!

Andrews Gyamfi
PLUS
Andrews Gyamfi
Courses Plus Student 15,658 Points
Andrews Gyamfi
Andrews Gyamfi
Courses Plus Student 15,658 Points

Hi Micah,

There are two issues with your for loop:

  • Firstly, you used the wrong punctuation just after your variable declaration inside the loop. Instead of a semi-colon you used a comma.

  • Secondly, your logic seem a bit flawed because you are increasing your counter variable (var i in this case) each time around the loop yet your condition states that the loop should run whilst var i is greater than the length of the temperatures array which would always be true (because you are increasing it from 0 to infinity). This would cause an infinite loop untill your computer runs out of memory: 

​var temperatures = [100,90,99,80,70,65,30,10];
for ( var i = 0, i > temperatures.length; i += 1 ) {
  console.log(temperatures[i]);
}

Change your code to that shown below and it should work fine: 

​var temperatures = [100,90,99,80,70,65,30,10];
for ( var i = 0; i < temperatures.length; i += 1 ) {
  console.log(temperatures[i]);
}

Cheers!

Marcus Parsons
Marcus Parsons
15,719 Points

Andrews,

Your solution is right on the money. But just to address the logic behind why the for loop doesn't execute: the for loop would never execute because the condition is false and i is of course not greater than the length of the array.

Andrews Gyamfi
Andrews Gyamfi
Courses Plus Student 15,658 Points

Hi Marcus,

That's perfectly right. The loop never gets executed as the first iteration would fail the conditional test. I was actually in a bit of a rush whilst replying to the question from my daytime workplace - haha! I call it "sneak coding". Thanks for picking that up though.

Cheers & happy coding!

Marcus Parsons
Marcus Parsons
15,719 Points

Cheers and happy coding to you, as well! :)

Jason Anders
MOD
Jason Anders
Treehouse Moderator 145,860 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,860 Points

Simple fix... You have i+=1 in your 'for' condition. Change it to i++ and you'll be good to go. :)