jQuery fadeTo() Method

Syntax:

$(selector).fadeTo(speed,opacity,callback);

The required opacity parameter in the fadeTo() method specifies fading to a given opacity (value between 0 and 1).

$("button").click(function(){
  $("#div1").fadeTo("slow",0.15);
  $("#div2").fadeTo("slow",0.4);
  $("#div3").fadeTo("slow",0.7);
});