How to obtain the URL uploaded by this file in multiple forms to implement javascript code _ javascript skills

Assume that a webpage contains multiple forms, one of which contains file uploads. The question is how to obtain the File Upload URL. Next we will introduce the implemented js Code, if you are interested, refer to the following: I hope you can help assume that a webpage contains multiple forms, one of which contains file uploads,

The Code is as follows:

...

The question is, how can I obtain the URL for uploading this file?
The following is an example of JavaScript code.

The Code is as follows:

Function showUploadUrl (){
For (var I = 0; I Var form = document. forms [I];
For (var j = 0; j If (form. elements [j]. type = "file "){
Alert ("Upload address:" + form. action );
}
}
}
}