怎么把JSON的多维数组转换成JS的多维数组

$.getJSON("../php/json.php?parm=arr2", function(json){
//中间应该怎么写
});

var arr1=["a","b","c"];
        var arr2=[
                ["a1","a2","a3"],
                ["b1","b2","b3"],
                ["c1","c2","c3"]
        ];
        var arr3=[
                 [
                    ["a11","a12","a13"],
                    ["a21","a22","a23"],
                    ["a31","a32","a33"]
                 ],
                 [
                    ["b11","b12","b13"],
                    ["b21","b22","b23"],
                    ["b31","b32","b33"]
                 ],
                 [
                    ["c11","c12","c13"],
                    ["c21","c22","c23"],
                    ["c31","c32","c33"]
                 ]
        ];