extjs 输入的小写在失去焦点之后变成大写

/**

     * 铁路货票号小写全部转成大写by hly 2013-12-03

     * @param {Object} invoiceValue

     */

    beforeChangeSmalLetterToBig : function(invoiceValue){

        var changeInvoiceNumber = invoiceValue;

        var afterInvioceNumber = '';

        for(var i =0 ;i< changeInvoiceNumber.length;i++ ){

             var regexp = /^[a-z]+$/;//小写字母

            if(regexp.test(changeInvoiceNumber[i])){//判断是否为小写字母by hly 2013-12-03

                afterInvioceNumber  += changeInvoiceNumber[i].toUpperCase();//如果是小写就转换成大写（根据客户要求所有小写转成大写）by hly 2013-12-03

            }else{

                afterInvioceNumber  += changeInvoiceNumber[i];

            }

            

        }

        return afterInvioceNumber;

    },