Question

I encounter some problem when I am trying to copy (non-duplicated) selected content from one listbox to another. I keep getting “Unable to get value of the property : object is null or undefined” exception.

Below are my codes

function CopyItem(from, to) {
    var src = document.getElementById(from);
    var dest = document.getElementById(to);

    for (var i = 0; i < src.options.length; i++) {
        if (src.options[i].selected) {
            var found = false;

            for (var j = 0; j < dest.options.length; j++) {
                if (dest.options[j].value == src.option[i].value) {
                    found = true;
                    break;
                }
            }

            if (!found) {
                var newOption = document.createElement("option");
                newOption.text = src.options[i].text;
                newOption.value = src.options[i].value;
                dest.options[dest.options.length] = newOption;
            }
        }
    }
}

@Html.ListBox("lvDataList", Model.DataList, new { id = "SelectionList", Multiple = "multiple", Size = 15, style = "width: 100%;" })
@Html.ListBoxFor(x => x.SelectedData, Model.SelectedDataList, new { id = "SelectedList", Multiple = "multiple", Size = 15, style = "width: 100%;" })
<input type="button" id="btnAdd" title="Add Selected Events" onclick="CopyItem('SelectionList', 'SelectedList', true)" />

Can someone please explain where did I code wrongly?
Thanks.

Answer 1

I guess you should have src.options instead of src.option in line

 if (dest.options[j].value == src.option[i].value) {