var arr = [

            ["a", "b"],

            ["1", "2"],

            ["d"]

        ];

        var sarr = [

            []

        ];

        for (var i = 0; i < arr.length; i++) {

            var tarr = [];

            for (var j = 0; j < sarr.length; j++)

                for (var k = 0; k < arr[i].length; k++)

                    tarr.push(sarr[j].concat(arr[i][k]));

            sarr = tarr;

        }

        alert(sarr.join("\n"));