Created
December 31, 2022 02:53
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A JavaScript function to detect the Media/Mime Type for a base64 string
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| /** | |
| * Returns the data type based on the base64 string | |
| * @param {String} base64String | |
| * @param {String} fileName | |
| * @returns {String} | |
| */ | |
| detectMimeType(base64String, fileName) { | |
| var ext = fileName.substring(fileName.lastIndexOf(".") + 1); | |
| if (ext === undefined || ext === null || ext === "") ext = "bin"; | |
| ext = ext.toLowerCase(); | |
| const signatures = { | |
| JVBERi0: "application/pdf", | |
| R0lGODdh: "image/gif", | |
| R0lGODlh: "image/gif", | |
| iVBORw0KGgo: "image/png", | |
| TU0AK: "image/tiff", | |
| "/9j/": "image/jpg", | |
| UEs: "application/vnd.openxmlformats-officedocument.", | |
| PK: "application/zip", | |
| }; | |
| for (var s in signatures) { | |
| if (base64String.indexOf(s) === 0) { | |
| var x = signatures[s]; | |
| // if an office file format | |
| if (ext.length > 3 && ext.substring(0, 3) === "ppt") { | |
| x += "presentationml.presentation"; | |
| } else if (ext.length > 3 && ext.substring(0, 3) === "xls") { | |
| x += "spreadsheetml.sheet"; | |
| } else if (ext.length > 3 && ext.substring(0, 3) === "doc") { | |
| x += "wordprocessingml.document"; | |
| } | |
| // return | |
| return x; | |
| } | |
| } | |
| // if we are here we can only go off the extensions | |
| const extensions = { | |
| xls: "application/vnd.ms-excel", | |
| ppt: "application/vnd.ms-powerpoint", | |
| doc: "application/msword", | |
| xml: "text/xml", | |
| mpeg: "audio/mpeg", | |
| mpg: "audio/mpeg", | |
| txt: "text/plain", | |
| }; | |
| for (var e in extensions) { | |
| if (ext.indexOf(e) === 0) { | |
| var xx = extensions[e]; | |
| return xx; | |
| } | |
| } | |
| // if we are here - not sure what type this is | |
| return "unknown"; | |
| } |
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