让底部页面始终居于底部 【jquery】

/*让底部页面始终居于底部*/
$(function() {
var Height1 = $('body').children().eq('1').height();
var Height2 = $('body').children().eq('2').height();
var Height3 = $('body').children().eq('3').height();
var Height4 = $('footer').height();


bottomHeight();


function bottomHeight() {
var goHeight = Height1 + Height2 + Height3;
var windowHeight = $(window).height();
if (goHeight < windowHeight) {
$('footer').css({
"position": "relative",
"top": "30px"
});
}
}
});