file-upload-component | React 16.0/Angular 1 | File Upload library

The problem is that when you pass the theme for second time with the folder2 value, the render code gets to execute before the theme effect executes moreover that it has a promise to resolve inside, thus render executes 2 times, one with the previous values and one with the new values but both with theme = 'folder2'. To overcome this issue, you'll have to use useLayoutEffect to clear the imageNames array. Doing so, there won't be a render with the previous values but with an empty array for the second render. Apparently there is a render occurring before useLayoutEffect, so to overcome this issue you can just setup a state variable to check if the current theme is equal to the selected theme; if it isn't you don't render the images, else if it is then render them; you'll set it to the theme after the image files are fetched and set: