The mouseup event occurs when the pointing device button is released.
It also occurs just before a click event.
event handler content attribute (ie on HTML attribute
<button class="btn btn-info" onmouseup="console.log('Mouse Up!')" >Hold me and release</button>
Example of DOM - Event Listener function with the mouseup event.
document.querySelector('button').addEventListener("mouseup", event => { console.log('Mouse Up!'); });
<button>Hold me and release</button>