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JavaScript JavaScript Loops, Arrays and Objects Simplify Repetitive Tasks with Loops For Loops

Posted by A X
A X
12,842 Points

Why doesn't my solution for Create a For Loop work?

From: https://teamtreehouse.com/library/javascript-loops-arrays-and-objects/simplify-repetitive-tasks-with-loops/create-a-for-loop

I've followed the logic outlined in the video preceding this code challenge and came up with this as a solution:

for (var i = 4; i <= 156; i + 1) {
  console.log(i);
}

Now this produced a fail on the code challenge, but I can't really determine why...the only things I can come up with is i is a reserved word, so I can't use it as a variable name. The other thought I had was that the sequence of the conditions in the parens matters, although this wasn't specified in the video. Either that or I have 'code blindness' and I can't see that I made a simple error. Can someone shed some light on this? Thanks!

1 Answer

Jason Anders
MOD
Jason Anders
Treehouse Moderator 145,858 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,858 Points

Hey Abby,

Nope, i is not reserved, so no need to worry there. :)

It's just a minor syntax error you have. Where are are incrementing the variable you have i + 1. When written this way, the compiler is seeing a mathematical expression and is expecting it to be assigned to another variable.

To add 1 to the variable (increment) you could do i += 1 or the more common (especially for a for loop) is i++ (make sure there are no spaces between the i and the ++.

for (var i = 4; i <= 156; i++) {
  console.log(i);
}

Hope that helps. Keep Coding! :dizzy:

Jason Anders
Jason Anders
Treehouse Moderator 145,858 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,858 Points

Oh, I forgot to mention. The order inside the parenthesis does matter, but you have it correct.

  1. Initial value

  2. Condition to meet

  3. Increment value

A X
A X
12,842 Points

Ah! I appreciate you explaining the difference between i + 1 vs. i ++ & i += 1. I also appreciate you explaining about i not being reserved. :) I also didn't know that there was a sequence to the parenthesis, so that's new and very useful information. So in the end, it was code blindness!

A X
A X
12,842 Points

This is a minor question, but I also wanted to ask then i += 1 will work as correct syntax i =+ 1 will not...can you expand upon why?

Jason Anders
Jason Anders
Treehouse Moderator 145,858 Points
Jason Anders
Jason Anders
Treehouse Moderator 145,858 Points

The += or =+ is one of those "just because." :)

I never really thought about it, but I'd guess that when the language was being built, that was the convention decided. I'm sure there is a logical reason (or maybe not).

When I first started JavaScript, I remembered which way it went by thinking is as "take the variable and add + [another value] to what you are already equal = to.

But as for a reason ... that like the question of why isn't "cat" spelled with a "k"? :smiley:

Sorry I don't have a more 'technical' answer for you. :dizzy: