WKWebView清理缓存

    NSArray * types =@[WKWebsiteDataTypeMemoryCache,WKWebsiteDataTypeDiskCache]; // iOS 9.0之后
    NSSet *websiteDataTypes = [NSSet setWithArray:types];
    NSDate *dateFrom = [NSDate dateWithTimeIntervalSince1970:0];
    [[WKWebsiteDataStore defaultDataStore] removeDataOfTypes:websiteDataTypes modifiedSince:dateFrom completionHandler:^{

    }];