function fooA(numOfRows: number, numOfCols: number) { const rows = new Array(numOfRows); return [...rows].map((_) => { const cols = new Array(numOfCols); return cols; }); } function fooB(numOfRows: number, numOfCols: number) { return [...Array(numOfRows)].map((_) => Array(numOfCols)); } function fooC(numOfRows: number, numOfCols: number) { const rows = new Array(numOfRows); return [...rows].map((_) => Array(numOfCols)); }