14.2.3自动切换焦点

(function(){//立即执行函数防止有全局变量
        function tabForward(event){
            event = EventUtil.getEvent(event);
            var target = EventUtil.getTarget(event);
            judge(target);
        }
        //判断
        function judge(target){
            // 判断目标内容的字符个数是否达到上限
            if (target.value.length === target.maxLength)
            {
                //h5的input的form属性
                var form = target.form;

                for (var i=0,len=form.elements.length;i<len ;i++ )
                {
                    //判断target是不是现在该有的元素
                    if (target === form.elements[i])
                    {
                        //判断下一个元素不为空
                        if (form.elements[i+1])
                        {
                            form.elements[i+1].focus();
                        }
                        return;
                    }
                }
            }
        }
        var textbox1 = document.getElementById('txtTel1');
        var textbox2 = document.getElementById('txtTel2');
        var textbox3 = document.getElementById('txtTel3');

        EventUtil.addHandler(textbox1,'keyup',tabForward);
        EventUtil.addHandler(textbox2,'keyup',tabForward);
        EventUtil.addHandler(textbox3,'keyup',tabForward);
    })()

此代码适合前面给出的标记，而且没有考虑隐藏字段