Cycling focus to the next item with a given tag or itemPath

TaskPaper
8

In any case, generalizing to item paths (rather than tag names), and allowing for indented projects (as well as full-left projects) a first draft might look something like:

Expand disclosure triangle to view JS source 
(() => {
    "use strict";

    // TaskPaper 3 focus cycled to the next item
    // matching a given item path.

    // Rob Trew @2022
    // Ver 0.01

    // --------------------- OPTIONS ---------------------

    // eslint-disable-next-line quotes
    const itemPath = '//project "—"';


    // ---------- TASKPAPER EVALUATION CONTEXT -----------

    const tp3Context = (editor, options) => {
        const outline = editor.outline;

        // All tasks on options.itemPath
        const
            cycleItems = outline.evaluateItemPath(
                `${options.itemPath}`
            );

        // Any current focus item, and its position,
        // if any, in the cycle.
        const
            maybeFocusedItem = editor.focusedItem,
            maybePosn = null !== maybeFocusedItem ? (
                cycleItems.findIndex(
                    x => maybeFocusedItem.id === x.id
                )
            ) : -1;


        // Zero-based index of next position in the cycle,
        // and the item at that index.
        const
            nextIndex = (1 + maybePosn) % cycleItems.length,
            nextFocusItem = cycleItems[nextIndex];

        return 0 < cycleItems.length ? (
            // Effect
            editor.focusedItem = nextFocusItem,
            // Value
            nextFocusItem.bodyContentString
        ) : `No items with with path ${options.itemPath}`;
    };

    // ------------- JXA EVALUATION CONTEXT --------------

    // main :: IO ()
    const main = () => {
        const
            doc = Application("TaskPaper")
            .documents.at(0);

        return doc.exists() ? (
            doc.evaluate({
                script: `${tp3Context}`,
                withOptions: {
                    itemPath
                }
            })
        ) : "No document open in TaskPaper.";
    };

    // MAIN ---
    return main();
})();