JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://raw.github.com/mikechambers/ExamplesByMesh/master/JavaScript/QuadTree/src/QuadTree.js"></script>
<div>
    <label>should show just cUL</label><div id="test1"></div>
    <label>should show cUR & cUR2:</label><div id="test2"></div>
</div>

JavaScript

$(function() {
    var worldBounds = {
        x: 0,
        y: 0,
        width: 100,
        height: 100
    };
    var quadTree = new QuadTree(worldBounds, true, 4, 2);

    var cUL = {
        x: 10,
        y: 10,
        name: "cUL"
    };
    quadTree.insert(cUL);

    var cUR = {
        x: 90,
        y: 10,
        name: "cUR"
    };
    var cUR2 = {
        x: 93,
        y: 13,
        name: "cUR2"
    };
    quadTree.insert(cUR);
    quadTree.insert(cUR2);
    
    var t1Rect = {
        x: 40,
        y: 40,
    };
    $.each(quadTree.retrieve(t1Rect), function(i, v) {
        $('#test1').append(v.name+" ");
    });
    
    var t2Rect = {
        x: 70,
        y: 20,
    };
    $.each(quadTree.retrieve(t2Rect), function(i, v) {
        $('#test2').append(v.name+" "); 
    });
});