有特定的字符串,如:如何獲得子特定字符
{"access_token":"TAeJxtzLtqwzAYQOG30WJkFFk3DxpCCKkhdUKdXcjSL2NqR0ayA3n7ZujQ0o7fGY4ZvbaESKuYw3XlJGbKc9w7FzCBPlBeMy4qj8yWk17j7OyKzCPoHeNUKkkIfTF_U1BFkdXTYqY4LJO9m21EXrvnDDnE6FHSgQbFgQRMhaeY1dLhXgDFsq93FqSvpKhR1gNEY71PkPPrFT-3pfybivPl1HS35tCZ63nftk17Kuw6l3lcwWRIj9HBLxT72_ulu74dP47Fz12CYcxrepb_RbTp2d7tAOkLEB1lYw2e3ddff00f03d82e9b36211220a974ae8b56c0263120c34a25a6c40c91a7f0fd","expires_in":179,"domain":"","username":"","firstname":"","lastname":"","email":"","roles":["","",""],"":true,"":
令牌的長度是動態的,同其他領域。我想要做的是提取子字符串TAeJxtzLtqwzAYQOG30WJkFFk3DxpCCKkhdUKdXcjSL2NqR0ayA3n7ZujQ0o7fGY4ZvbaESKuYw3XlJGbKc9w7FzCBPlBeMy4qj8yWk17j7OyKzCPoHeNUKkkIfTF_U1BFkdXTYqY4LJO9m21EXrvnDDnE6FHSgQbFgQRMhaeY1dLhXgDFsq93FqSvpKhR1gNEY71PkPPrFT-3pfybivPl1HS35tCZ63nftk17Kuw6l3lcwWRIj9HBLxT72_ulu74dP47Fz12CYcxrepb_RbTp2d7tAOkLEB1lYw2e3ddff00f03d82e9b36211220a974ae8b56c0263120c34a25a6c40c91a7f0fd
所以,作爲subString函數的第二個參數必須提供什麼標識該字符串中的第一個「,」。任何人可以幫忙?