JSFiddle - React, Tailwind, and code Playground

HTML

<div class="boundary">1</div>

<div class="boundary0">0</div>

CSS

.boundary, .boundary0 {
     width: 100px;
 height: 100px;
 background: silver;   
}

JavaScript

$(document).ready(
    function () {
        var state = {flag: false};
        $('.boundary').mousedown(function () {
            state.flag = true;
            console.log(state);
        });
        $('.boundary0').mouseup(function () {
            state.flag = false;
            console.log(state);
        });
    }
)