How to insert data into lookup column using javascript

Question

I have created a custom drop-down list and inserting drop-down data into lookup column(in a list).

How to insert drop down data into a look up column?

I am trying below code but it is not working.

oListItem.set_item('SupportCategoryName', ddlgrpname);

Answer 1

Please try following code. It is perfectly working code. Here "valToBeInsertd" is varible name.

function InsertIntoLookUp()
{

    var itemCreationInfo = new SP.ListItemCreationInformation();
    oListItem = list.addItem(itemCreationInfo);

    var selectedText = valToBeInsertd;


    oListItem.set_item('Name', "-1;#" + selectedText); 
    oListItem.update();  
    context2.load(oListItem); 
    context2.executeQueryAsync(SuccessInsertIntoLookUp, FailInsertIntoLookUp); 
}
function SuccessInsertIntoLookUp()
{
    alert("inserted....");
}
function FailInsertIntoLookUp()
{
    alert("failed to insert into lookup");      
}

Answer 2

Use SP.FieldLookupValue

  var lookupSingle = new SP.FieldLookupValue();  
  lookupSingle.set_lookupId(theIdHere);  
  oListItem.set_item('SupportCategoryName', lookupSingle); 

Answer 3

var e = document.getElementById('<%=ddlgrpname.ClientID%>');
var ddlgrpname = e.options[e.selectedIndex].value;
oListItem.set_item('SupportCategory', ddlgrpname);