JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="categories">
   <li data-category="category-1">Category 1</li>
   <li data-category="category-1">Category 1</li>
   <li data-category="category-1">Category 1</li>
   <li data-category="category-1">Category 1</li>
   <li data-category="category-1">Category 1</li>
   <li data-category="category-2">Category 2</li>
   <li data-category="category-2">Category 2</li>
   <li data-category="category-2">Category 2</li>
   <li data-category="category-3">Category 3</li>
</ul>

JavaScript

var cat1 = [];
var cat2 = [];
var cat3 = [];

$('li').each(function () {

var attrvalue = $(this).attr('data-category');

if (attrvalue == "category-1") { 
    cat1.push(attrvalue);
}

if (attrvalue == "category-2") { 
    cat2.push(attrvalue); 
}

if (attrvalue == "category-3") { 
    cat3.push(attrvalue);
} 
});

console.log('how many are here? :'+ cat1);
console.log('how many are here? :'+ cat2);
console.log('how many are here? :'+ cat3);