JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="ul1">
  <li id="1">ul1-1</li>
  <li id="2">ul1-2</li>
  <li id="3">ul1-3</li>
</ul>

<ul id="ul2">
  <li id="1">ul2-1.1</li>
  <li id="2">ul2-2.2</li>
</ul>

JavaScript

const array1 = $( document ).find( '#ul1' ).find( 'li' ).get();
const array2 = $( document ).find( '#ul2' ).find( 'li' ).get();

let array3;

if($( array1 ).length > $( array2 ).length) {
  array3 = array1.filter(item => !array2.find(search => search.id === item.id));
}

console.log(array3);