When I implement this function as js code, I don't know how to create a byte array. The function read of InputStream need byte array as first arg. More on github.com

For a proper answer that will let you understand this topic in depth you would need to look into a different programming language like C. Javascript is a bit too high level (meaning it hides details from you) so you are left with incomplete picture. That being said - are you familiar with binary system? Aka 0s and 1s. A single byte is built of 8 bits (aka individual digits). For instance 11 is 3 (20 + 21 ), 11011 is 27 (1+2+8+16). Meaning that byte can have a maximum value of 255 (11111111, 1+2+4+8+16+32+64+128). Now, integers are much bigger than individual bytes. This depends HEAVILY on a platform you are working on (64-bit vs 32-bit system, little microcomputers vs full fledged PCs) but in general you can expect Integer to hold at least 4 bytes in most situations. That's up to 11111111 11111111 11111111 11111111 (4294967295 in our human friendly system). This means that a single integer takes 4x as much space in memory as a single byte. Why is this important? Because memory concerns while much lower nowadays are still not to be ignored. Example - you have a FullHD movie. That's 1920x1080 pixels (2073600 total). Now, a single pixel can be defined with values RGB (red, green, blue) ranging from 0 to 255. Meaning that without any compression a frame takes 2073600 x 3 bytes = 6220800 bytes. That's 5 MB/s per frame or 150MB/s (assuming 30 fps). If you used integers for some reason (and only used their first byte since max value is still 255, just that it looks like 00000000 00000000 00000000 11111111 in memory) you now need 3x more memory. Realistically it could go even higher cuz save for colours you might also have an Alpha (transparency) layer. As for text: Does it look at every X numbers and perform an operation? With ASCII it would be the case. Here's ASCII: http://www.asciitable.com/ Long story short - each character IS actually a number to a computer. We just chose to display value of 65 as 'A' for instance. You might as well make up your own system that takes an integer and prints 'F' when it's value is 30. But this would be insanely messy if everyone tried that so we have made official standards over the years. It's actually not that simple as individual characters in UTF8 are NOT of fixed size. In fact there are 3 specific ways on looking at characters: one is at individual bytes second is scalar values. This is what a character is made of. last is graphene clusters. This is what we humans consider to be complete characters. With english it's not that important but well, UTF-8 is supposed to take all characters existing, not just english ones. Here's a somewhat trollish example: 💩 This thing is actually made of more than one individual byte. Alone they don't make sense and can't even be displayed (you can't even save a reddit post with them separately), only together they create poo. Another sample is नमस्ते. Which consists of byte values [224, 164, 168, 224, 164, 174, 224, 164, 184, 224, 165, 141, 224, 164, 164,224, 165, 135] and scalar values ['न', 'म', 'स', '्', 'त', 'े'] (I shamelessly used Rust programming language explanation from here: https://doc.rust-lang.org/book/second-edition/ch08-02-strings.html ). Here's a good explanation on UTF-8: https://www.youtube.com/watch?v=MijmeoH9LT4 But let's just put it this way - there's a lot of magic going behind your back when it comes to characters encoding. Javascript hides a lot of it from you (which is why I said at the very beginning you would need to try out a lower level one) but sometimes it has to expose these functions to you directly. More on reddit.com

I’m about to grossly misuse JavaScript with this in hand. More on reddit.com