Use the FileUploadField plug-in of Extjs to upload files. Because FileUploadField is an extension plug-in of ext, its method cannot be found in its API. This file is in ux under the examples folder of extjs, so it must be used when using FileUploadField. It can be used only after it is imported. A problem that will arise during use is that two upload buttons appear on the page. This is related to the CSS style of ext itself, so the style needs to be modified: