When the mouse button is released over an element, the onmouseup event triggers. You can try to run the following code to implement onmouseup attribute −
Example
<!DOCTYPE html> <html> <body> <h3 id = "myid" onmousedown = "mouseDown()" onmouseup = "mouseUp()"> This is demo heading. </h3> <p>Click above and then release.</p> <script> function mouseDown() { document.getElementById("myid").style.color = "yellow"; } function mouseUp() { document.getElementById("myid").style.color = "blue"; } </script> </body> </html>