Set Lookup Value using Javascripts in CRM

function set_LookupValue(fieldName, id, name, entityType) {

        if (fieldName != null && id != null) {

            var lookupValue = new Array();

            lookupValue[0] = new Object();

            lookupValue[0].id = id;

            lookupValue[0].name = name;

            lookupValue[0].entityType = entityType;

            Xrm.Page.getAttribute(fieldName).setValue(lookupValue);

        }

    }