Page History

<script>
    $(function(){
            var orig_pool = []; // we will keep a copy of "removed" element for restoring later
            var hot = FormUtil.getField("field1").data("hot");
            source = hot.getSettings()['columns'][1]['source']; // we get all the dropdown option from column #1 of the table ("Continent"), call it "source"
                                                                // p.s, column count starts from 0. so column #1 = second column
                                                                
            hot.addHook('afterChange', function(change,type){   // set a hook / event listener to trigger after any change on the table
                if(type == 'edit'){ // if the change type is of type "edit", we proceed
                    data = {    // prepare the data object
                        source : source, 
                        change : change,
                        orig_pool : orig_pool
                    }
                    if(change[0][3] != ''){ removeSource(data); }   // if the changed value is not empty, we remove the data from the "source"
                    else{ addSource(data); }    // otherwise, the change value is empty, meaning it is removed from the table
                                                // we need to add it back to the "source"
                }
            })
          
    })
    
    function removeSource(data){
        slice_index = data.source.indexOf(data.change[0][3]);   // find the index of the continent in the "source" array
        data.orig_pool.push(data.source.slice(slice_index,slice_index + 1)); // copy this value to our "original pool" of country
                                                                             // for use later in addSource()
        data.source.splice(data.source.indexOf(data.change[0][3]),1);   // splice the value out from "source" array
    }
    
    function addSource(data){
        data.orig_pool.splice(data.source.indexOf(data.change[0][2]),1) // splice the value out from "original pool" array
        if(data.change[0][2] != ''){    // if the initial value of the cell is not empty,
            data.source.push(data.change[0][2]);    // we add the value back to "source" array
            data.source.sort(); // sort the source array so it looks nice.
        }
    }
</script>