if button click javascript code example

Example 1: detect button click jquery

$(".btn").click(function(){
  var clk = $(this).attr("id");
});

Example 2: if mousepressed javascript

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