Pascal's Triangle

var generate = function(numRows) {
    var rows = [];
    for (var row = 1; row <= numRows; row++) {
        rows.push([]);
        var rowIndex = row - 1;
        var numOfItems = row;
        
        for (var itemNum = 1; itemNum <= numOfItems; itemNum++) {
            if (itemNum === 1 || itemNum === numOfItems) {
                rows[rowIndex].push(1);
            } else {
                var lastRow = rowIndex - 1;
                var currentNum = rows[lastRow][itemNum - 2] + rows[lastRow][itemNum - 1];
                rows[rowIndex].push(currentNum);
            }
        }
        
    }
    return rows;
}