function swapImg() {  $(".hover").each(function() {    var normal = this.src;    var dot = this.src.lastIndexOf('.');    var hover = this.src.substr(0, dot) + '_on' + this.src.substr(dot, 4);    $(this).hover(      function() { this.src = hover; },      function() { this.src = normal; });  });}$(document).ready(swapImg);