javascript - 文件上传时如何编辑CSS(How to edit css when file is uploaded)

Question

I have a form where users can upload a file.(我有一个表单，用户可以在其中上传文件。)

The uploading and validation afterwards (filesize, filetype...) is done with php by submitting.(之后，上传和验证（文件大小，文件类型...）是通过php通过提交完成的。) But I wonder how I could give the user a "visual feedback" that his file was "picked" immediately.(但是我不知道如何给用户一个“视觉反馈”，即他的文件被“挑选”。) So I don't need validation nor anything complex.(因此，我不需要验证，也不需要任何复杂的操作。) I just want to either color the label green or rename the label of the upload field when the user has selected a file and clicked "Choose" in his browser.(当用户选择文件并在浏览器中单击“选择”时，我只想为标签涂上绿色或重命名上载字段的标签。) How would I do that most easily?(我将如何最轻松地做到这一点？)   ask by Daiaiai translate from so

Answer 1

成功后，分配一个变量，然后使用该变量将类添加到元素。