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I want to change the background of all list items. I have this but it doesn't work.

// Get all <li> elements in the document
var x = document.querySelectorAll("li"); 

for (let i = 0; < x.length; i++;) {

x[i].style.backgroundColor = "red"; 
}

I want to change the background of all list items. I have this but it doesn't work.

// Get all <li> elements in the document
var x = document.querySelectorAll("li"); 

for (let i = 0; < x.length; i++;) {

x[i].style.backgroundColor = "red"; 
}

• javascript
• jquery

Share Improve this question Follow edited Apr 2, 2018 at 0:32 verlager asked Apr 2, 2018 at 0:29 verlagerverlager 87655 gold badges2626 silver badges4848 bronze badges 1

• 1 you dont need to do a loop just assign a css to the li example $('li').addClass('red') where class red has style background red – guradio Commented Apr 2, 2018 at 0:32

Add a ment  | 

7 Answers 7

Sorted by: Reset to default 5

Typo Error:

Replace for (let i = 0; < x.length; i++;) with for (let i = 0; i < x.length; i++)

Yet another typo: ; after i++

Your JS is correct, it's just having a typo.

var x = document.querySelectorAll("li");

for (let i = 0; i < x.length; i++) {
  x[i].style.backgroundColor = "red";
}

li {
  color: white;
  text-align: center;
  border: 1px solid white;
  font-weight: 900;
}

<ul>
  <li>YOUR</li>
  <li>JAVASCRIPT</li>
  <li>IS</li>
  <li>WORKING</li>
</ul>

Use this:

var lists = document.getElementsByTagName("li");

// Var or Let works in the for loop

for(let list in lists) {
    lists[list].style.backgroundColor = "black";
}

Not jQuery but basic JavaScript

You made a typo error, here the correct one:

var x = document.querySelectorAll("li"); 

for (let i = 0; i < x.length; i++) {
    x[i].style.backgroundColor = "red"; 
}

Another solution:

x.forEach((li) => li.style.backgroundColor = "red");

Another approach is to use a little css and Javascript.

CSS:

.red{
    background-color:red
}

jQuery:

$('li').addClass('red')

The jquery then adds a class of red to all li elements. In the included example I changed the selector so that it only changes the styling of the desired list. In case there are multiple lists on the page.

$('ol.selected li').addClass('red')

.red{
        background-color:red
    }

<script src="https://ajax.googleapis./ajax/libs/jquery/2.1.1/jquery.min.js"></script>

<ol>
  <li>List item one</li>
  <li>List item two</li>
  <li>List item three</li>
</ol>

<ol class='selected'>
  <li>List item one</li>
  <li>List item two</li>
  <li>List item three</li>
</ol>

using Jquery, the following line will do the trick. $("li").css("background-color","red");

Hope this helps

Use

Array.
  from(document.getElementsByTagName("li"))
  .map(e => e.style.backgroundColor = "black");

or use

[]
  .slice
  .call(document.getElementsByTagName("li"))
  .map(e => e.style.backgroundColor = "black");

You might consider to use forEach, instead of map according to your taste.

P.S. There are plenty of resources explaining execution time and other acpects between two of them.

You can refactor the code using a forEach loop to make it way easier.

let x = document.querySelector("li");
x.forEach(function(listElement){
this.style.background = "red";
]);

Thats the easiest non-jquery way of doing this. Picture it like this, a for each loop, is basically saying this: "Ok, so for each list element, I want the background to be red".

Hope that helped, - Sami

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