How to Set the value of a lookup field using javascript in MS CRM

 Set the value of a lookup field

var lookup = new Array();
lookup[0] = new Object();
lookup[0].id = recorid;
lookup[0].name = recordname;
lookup[0].entityType = entityname;
Xrm.Page.getAttribute("fieldSchemaname").setValue(lookup);

Alternate way to Set the value of a lookup field

Xrm.Page.getAttribute("fieldSchemaname").setValue([{ id: recorid, name: recordname, entityType: entityname}]);