遮罩层

var Json = {
zhebg: function() {
var div = $("<div>").addClass("div_obj");
console.log(div);
$("body").append(div);
var div_obj = $(".div_obj");
var height = document.body.clientHeight;
div_obj.css({
'position': 'fixed',
'left': '0',
'top': '0',
'background': 'rgba(0,0,0,0.3)',
'width': '100%',
'height': height
});
}
}