layui的select事件，为什么使用form.on监听事件浏览器会提示form.on is not a function？

<select name="province" id="province" lay-filter="business" lay-verify="type" >

layui.use('form', function(){
	var form = layui.form();
	form.on('select(business)', function() {
		alert(2);
	});
	return form;
});

可能对应着layui版本不同，var form = layui.form();或者var form = layui.form;切换即可解决问题