Function createOrUpdateItem

src/chart/custom/CustomView.ts:963–995

(
    api: ExtensionAPI,
    existsEl: Element,
    dataIndex: number,
    elOption: CustomRootElementOption,
    seriesModel: CustomSeriesModel,
    group: ViewRootGroup,
    data: SeriesData<CustomSeriesModel>
)

}

function createOrUpdateItem(
    api: ExtensionAPI,
    existsEl: Element,
    dataIndex: number,
    elOption: CustomRootElementOption,
    seriesModel: CustomSeriesModel,
    group: ViewRootGroup,
    data: SeriesData<CustomSeriesModel>
): Element {
    // [Rule]
    // If `renderItem` returns `null`/`undefined`/`false`, remove the previous el if existing.
    //     (It seems that violate the "merge" principle, but most of users probably intuitively
    //     regard "return;" as "show nothing element whatever", so make a exception to meet the
    //     most cases.)
    // The rule or "merge" see [STRATEGY_MERGE].

    // If `elOption` is `null`/`undefined`/`false` (when `renderItem` returns nothing).
    if (!elOption) {
        group.remove(existsEl);
        return;
    }
    const el = doCreateOrUpdateEl(api, existsEl, dataIndex, elOption, seriesModel, group);
    el && data.setItemGraphicEl(dataIndex, el);

    el && toggleHoverEmphasis(
        el,
        elOption.focus,
        elOption.blurScope,
        elOption.emphasisDisabled
    );

    return el;
}

function doCreateOrUpdateEl(
    api: ExtensionAPI,