p5 editor mouse press down code example

Example 1: if mousepressed javascript

var mouseDown = 0;
document.body.onmousedown = function() { 
  ++mouseDown;
}
document.body.onmouseup = function() {
  --mouseDown;
}

Example 2: p5 on mouse press

function mousePressed() {
  ellipse(mouseX, mouseY, 5, 5);
  // prevent default
  return false;
}