[String.prototype.substring](https://link.segmentfault.com/?enc=feOKVC5mbGZDjMca4UktMw%3D%3D.tLmeVQpogGE0B5205DwNs19Na2B3v6BQTQuE3aRAcvLIwQeRiaoNBstCawwCVDMdlV50GhIjOOqQ%2BknnLJRK3zghpraqcaHNt%2B5sHvw%2F003xJ4lOwtkv3kDBONbfylg7Ug%2Fs1ZUS1C2YsovKuKk2Ld4YtD8%2FMjIo2GpCMDpx0IESozHCadVIzodccjpBEYq7XTbBB%2FuyGPyzhGg%2BJD25iaDM87PpP1TvGNyiizb9cYA%3D)  