1. self.webView.UIDelegate = self;

2. 实现代理在本地打开NSOpenPanel，并将解决回调回去

- (void)webView:(WKWebView*)webView runOpenPanelWithParameters:(WKOpenPanelParameters*)parameters initiatedByFrame:(WKFrameInfo*)frame completionHandler:(void(^)(NSArray *_NullableURLs))completionHandler{

    NSOpenPanel* panel = [NSOpenPanel openPanel];

    if(@available(macOS10.12, *)){

        panel.allowsMultipleSelection = parameters.allowsMultipleSelection;

    }else{

        [panelsetAllowsMultipleSelection:NO];  //是否允许多选file

    }

    if(@available(macOS10.13.4, *)){

        panel.canChooseDirectories = parameters.allowsDirectories;

    }else{

        panel.canChooseDirectories=NO;  //是否允许选目录

    }

    panel.allowedFileTypes = @[@"png", @"jpg", @"BMP", @"TIFF"];//图片类型

    NSModalResponseresult = [panelrunModal];

    if(result ==NSModalResponseOK){

        completionHandler([panelURLs]);

    }else{

        completionHandler(nil);

    }

//    [panel beginWithCompletionHandler:^(NSModalResponse result) {

//        if (result == NSModalResponseOK) {

//            completionHandler([panel URLs]);

//        }

//    }];

}