//默认选中下拉列表
    function checkOption(id,value){
        var select = document.getElementById(id);
        var options = select.options;
        for(var i=0;i<options.length;i++){
            if (options[i].value =http://www.mamicode.com/= value){
                options[i].selected = true;
                break;
            }
        }
    }