Thank you hukka, ill try the code.
I can say i' m satisfied. I put 3 threads at work and now it works like a charm, it loads all the images in less than 3 seconds. It's perfect for me. About my app in electron, i have forgotten a couple of things(i coded it a while ago). First of all i load only the images in the visible area and i load the rest incrementally while scrolling down. But more importantly, javascript has only one thread, so you cannot use multi-threading, but it has a cool feature called the event-loop(i think it's called like that), which means that I/O operations(like the loading of images, net or database connections and so on) happen by default not in the main thread(like it is for free pascal and most languages and that's why you need multi threading) but somewhere else and when the process ends you get notified through the use of callbacks. So we could say that javascript is non-blocking or async by nature. That's why it looks so smooth. Now i remember that when i loaded all the images at once there was a noticeable delay, although it is non-blocking!! That's why i decided to load only the images in the visible part of the app!