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JavaScript JavaScript Loops, Arrays and Objects Tracking Multiple Items with Arrays Using For Loops with Arrays

Gary Calhoun
Gary Calhoun
10,317 Points
Posted by Gary Calhoun
Gary Calhoun
10,317 Points

We created a variable for <ol> but not <li>?

I was just trying to understand why we didn't create a variable for the <li> tag but we did for the <ol> tag or is just because we have to have a variable to print so it could of been anything?

function printList( list) {
  var listHTML = '<ol>';
  for ( var i = 0; i < list.length; i += 1 ) {
    listHTML += '<li>' + list[i] + '</li>';
  }
  listHTML += '</ol>';
  print(listHTML);
}
printList(playList);

2 Answers

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

Hi Gary. I think the purpose of creating the variable is to store the concatenation of the completed string. In real life, you wouldn't have had to assign the ol tag to the variable to have it still work.

You could have declared an empty string variable and just started the concatenating with the ol tag. For example: 

function printList( list) {
  var listHTML "";                    //declare an empty string
  for ( var i = 0; i < list.length; i += 1 ) {
    listHTML = '<ol>' += '<li>' + list[i] + '</li>';                 //added the <ol> tag to the concatenated string
  }
  listHTML += '</ol>';
  print(listHTML);
}
printList(playList);

So, it's not that one tag was declared and not the other, it was just a programming choice to start the variable with the ol tag already declared. In my opinion, neither way is better than the other in syntax or DRY programming; however, the one with the ol tag declared in the variable would be easier to figure out if you were looking at the code and not the original programmer.

Make sense? I hope so.

Keep Coding! :)

Gary Calhoun
Gary Calhoun
10,317 Points
Gary Calhoun
Gary Calhoun
10,317 Points

Thanks yes makes perfect sense now:)

Diego Caballero de Alba
Diego Caballero de Alba
11,507 Points
Diego Caballero de Alba
Diego Caballero de Alba
11,507 Points

The only problem with this is that the <ol> tag is inside the for loop and it has to be outside!

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

Ah, yes Diego, you are correct. I guess I was too tied up in declared and empty variables that I wasn't paying attention to the loop and its purpose.

Good Catch! :)

Julian Gutierrez
Julian Gutierrez
19,201 Points
Julian Gutierrez
Julian Gutierrez
19,201 Points

In this example the variable isn't only holding the ordered list "ol". It's being used to store the concatenated html being produced by running through the loop. The variable will end up storing something similar to the below html without the comments.

<ol> <!-- Initial variable declaration -->
<li>List item 1</li> <!-- First iteration of loop -->
<li>List item 2</li> <!-- Second iteration of loop -->
<li>List item 3</li> <!-- Third iteration of loop -->
</ol> <!-- Added after the escaping the for loop -->