How to lock only dedicated cells via Excel JavaScript API

As documented here I tried to lock only some cells (all cells of a column in my case) but all cells of the whole document are locked and not only the cells of the range. I already tried to lock only some cells like "D1:D5" but again all cells are locked and not only these 5 cells.

This is my code:

function lockColumnHandler() {
    lockColumn("Sheet1", "D:D");
}

function lockColumn(sheetName, columnRange) {
    Excel.run(function (ctx) {
        var sheet = ctx.workbook.worksheets.getItem(sheetName);
        var range = sheet.getRange(columnRange);

        if (range) {
            range.format.protection.locked = true;
        }

        sheet.protection.protect({
            allowAutoFilter: true,
            allowDeleteColumns: true,
            allowDeleteRows: true,
            allowFormatCells: true,
            allowFormatColumns: true,
            allowFormatRows: true,
            allowInsertColumns: true,
            allowInsertHyperlinks: true,
            allowInsertRows: true,
            allowPivotTables: true,
            allowSort: true
        });

        return ctx.sync();
    })
    .catch(errorHandler);
}