function zoom(mask, bigimg, smallimg) {
	this.bigimg = bigimg;
	this.smallimg = smallimg;
	this.mask = mask
}
zoom.prototype = {
	init: function() {
		var that = this;
		this.smallimgclick();
		this.maskclick();
		this.mousewheel()
	},
	smallimgclick: function() {
		var that = this;
		$("." + that.smallimg).click(function() {
			$("." + that.bigimg).css({
				width: $("." + that.smallimg).width() * 2
			});
			$("." + that.mask).fadein();
			$("." + that.bigimg).attr("src", $(this).attr("src")).fadein()
		})
	},
	maskclick: function() {
		var that = this;
		$("." + that.mask).click(function() {
			$("." + that.bigimg).fadeout();
			$("." + that.mask).fadeout()
		})
	},
	mousewheel: function() {
		function mousewheel(obj, upfun, downfun) {
			if (document.attachevent) {
				obj.attachevent("onmousewheel", scrollfn)
			} else {
				if (document.addeventlistener) {
					obj.addeventlistener("mousewheel", scrollfn, false);
					obj.addeventlistener("dommousescroll", scrollfn, false)
				}
			}

			function scrollfn(e) {
				var ev = e || window.event;
				var dir = ev.wheeldelta || ev.detail;
				if (ev.preventdefault) {
					ev.preventdefault()
				} else {
					ev.returnvalue = false
				} if (dir == -3 || dir == 120) {
					upfun()
				} else {
					downfun()
				}
			}
		}
		var that = this;
		mousewheel($("." + that.bigimg)[0], function() {
			if ($("." + that.bigimg).innerwidth() > $("body").width() - 20) {
				alert("不能再放大了");
				return
			}
			if ($("." + that.bigimg).innerheight() > $("body").height() - 50) {
				alert("不能再放大");
				return
			}
			var zoomheight = $("." + that.bigimg).innerheight() * 1.03;
			var zoomwidth = $("." + that.bigimg).innerwidth() * 1.03;
			$("." + that.bigimg).css({
				height: zoomheight + "px",
				width: zoomwidth + "px"
			})
		}, function() {
			if ($("." + that.bigimg).innerwidth() < 100) {
				alert("不能再缩小了哦！");
				return
			}
			if ($("." + that.bigimg).innerheight() < 100) {
				alert("不能再缩小了哦！");
				return
			}
			var zoomheight = $("." + that.bigimg).innerheight() / 1.03;
			var zoomwidth = $("." + that.bigimg).innerwidth() / 1.03;
			$("." + that.bigimg).css({
				height: zoomheight + "px",
				width: zoomwidth + "px"
			})
		})
	}
};