Jquery 작업 select 매듭

<select class="form-control selOP" placeholder="Pick Orchestration Plan">

      <option value="" disabled selected style='display:none;'>Pick Orchestration Plan</option>

      <option value="Residential">Quad Play</option>

      <option value="Residential West">Plan 1</option>

</select>

$("#select_id").change(function(){

    //code...

});

var checkText=$("#select_id").find("option:selected").text(); //  Select   Text
//var $(#testSelect option:selected').text();

var checkValue=$("#select_id").find("option:selected").val(); //  Select   Value

var checkIndex=$("#select_id ").get(0).selectedIndex;         //  Select       

var maxIndex=$("#select_id option:last").attr("index");       //  Select      

$("#select_id ").get(0).selectedIndex=1; //  Select    1    

$("#select_id ").val(4);                 //  Select Value  4    

$("#select_id option[text='jQuery']").attr("selected", true); //  Select Text  jQuery     

$("#select_id").append("<option value='Value'>Text</option>");   // Select    Option(   )

$("#select_id").prepend("<option value='0'>   </option>");     // Select    Option(     )

$("#select_id option:last").remove();        //  Select      Option(    )

$("#select_id option[index='0']").remove(); //  Select     0 Option(   )

$("#select_id option[value='3']").remove(); //  Select Value='3' Option

$("#select_id option[text='4']").remove();  //  Select Text='4' Option 

function changeShipMethod(shipping){

　　var len = $("select[@name=ISHIPTYPE] option").length；

　　if(shipping.value != "CA"){

　　　　$("select[@name=ISHIPTYPE] option").each(function(){

　　　　　　if($(this).val() == 111){

　　　　　　$(this).remove();

　　　　}

　　　　});

　　}else{

　　　　$("<option value='111'>UPS Ground</option>").appendTo($("select[@name=ISHIPTYPE]"));

　　}

} 

$("#sel").empty()；
document.all.objSelect.options.length = 0;  

$("#txt").attr("value",'');//    

$("#txt").attr("value",'11');//     

$("#chk1").attr("checked",'');//   

$("#chk2").attr("checked",true);//  

if($("#chk1").attr('checked')==undefined) //         

$("input[@type=radio]").attr("checked",'2');//  value=2          

$("#sel").attr("value",'-sel3');//  value=-sel3         

$("<option value='1'>1111</option><option value='2'>2222</option>").appendTo("#sel")//      option