CODEWITHSUNDEEP
javascripthtmldomhtml-lists
neil
neil

Reputation: 1306

JavaScript: splitting an HTML list in half

I have a 26-item list with one for each letter of the alphabet

<ul>
  <li id="a">A</li>
  ...
  <li id="m">M</li>
  <li id="n">N</li>
  ...
  <li id="z">Z</li>
</ul>

How could I use JavaScript to terminate the list after 'M' (i.e. </ul>, add an <h2> element and start another list, beginning with 'N'?

So:

<ul>
  ...
  <li id="m">M</li>
</ul>
<h2>Part 2</h2>
<ul>
  <li id="n">N</li>
  ...
</ul>

I can insert the h2 element fine with .createElement and .insertBefore, but I can't get the closing and opening list tags either side of it. I've tried innerHTML, outerHTML, insertBefore...

Upvotes: 4

Views: 551

Answers (2)

Oriol
Oriol

Reputation: 288500

You can get the ul, clone it, insert the clone, and append the childnodes of the ul after the 13th child element to the clone:

var ul = document.querySelector('ul'),
    newUl = ul.cloneNode(false),
    last = ul.children[12];
ul.parentNode.insertBefore(newUl, ul.nextSibling);
ul.parentNode.insertBefore(document.createElement('h2'), newUl)
  .appendChild(document.createTextNode('Part 2'));
while(last.nextSibling) newUl.appendChild(last.nextSibling);


var ul = document.querySelector('ul'),
    newUl = ul.cloneNode(false),
    last = ul.children[12];
ul.parentNode.insertBefore(newUl, ul.nextSibling);
ul.parentNode.insertBefore(document.createElement('h2'), newUl).appendChild(document.createTextNode('Part 2'));
while(last.nextSibling) newUl.appendChild(last.nextSibling);
<ul>
  <li id="a">A</li>
  <li id="b">B</li>
  <li id="c">C</li>
  <li id="d">D</li>
  <li id="e">E</li>
  <li id="f">F</li>
  <li id="g">G</li>
  <li id="h">H</li>
  <li id="i">I</li>
  <li id="j">J</li>
  <li id="k">K</li>
  <li id="l">L</li>
  <li id="m">M</li>
  <li id="n">N</li>
  <li id="o">O</li>
  <li id="p">P</li>
  <li id="q">Q</li>
  <li id="r">R</li>
  <li id="s">S</li>
  <li id="t">T</li>
  <li id="u">U</li>
  <li id="v">V</li>
  <li id="w">W</li>
  <li id="x">X</li>
  <li id="y">Y</li>
  <li id="z">Z</li>
</ul>

Upvotes: 1

Richard Hamilton
Richard Hamilton

Reputation: 26444

The array#slice method doesn't work on DOM elements. We will have to iterate through all of the elements, and create a new array instead.

First we have to remove the original list from the DOM. We can do that with the removeChild function

var originalList = document.getElementById("existingList");
document.body.removeChild(orginalList);
# Or wherever your list was nested under

# find all your list elements. This is assuming you only have 26 list elements
var li = document.getElementsByTagName("li");
var firstLetters, secondLetters = [], [];

# Create array for first half of list elements
for (var i = 0; i < li.length/2; i++) {
  firstLetters.push(li[i]);
}

# Create array for second half of list elements
for (var i = li.length/2; i < li.length; i++) {
  secondLetters.push(li[i]);
}

var list1 = document.createElement("ul");
var list2 = document.createElement("ul");

document.body.appendChild(list1);
document.body.appendChild(list2);

for (var i = 0; i < firstLetters.length; i++) {
  list1.appendChild(firstLetters(i));
}

for (var i = 0; i < secondLetters.length; i++) {
  list2.appendChild(secondLetters(i));
}

Upvotes: 3

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