isInArray = function (arr, obj) {
                if (!arr[obj[0]])
                    arr[obj[0]] = { normals: [], idx: [] };
                var idx = arr[obj[0]].normals.indexOf(obj[1]);
                return idx === -1 ? -1 : arr[obj[0]].idx[idx];
            }
Search for obj in the given array.
This function is called to check if a couple of data already exists in an array.

If found, returns the index of the founded tuple index. Returns -1 if not found
@param arr Array<{ normals: Array<number>, idx: Array<number> }>
@param obj Array<number>
@returns {boolean}