Java byteArray equivalent in JavaScript

Question

I am trying to determine what encoding scheme will give me the numbers -1 or -40 (the starting numbers for the file) for a jpeg file type.

A rest api I'm working on is expecting a byte array that looks like [-1, 94, 43, 34, etc]. In node.js I can have the byte array as hex, or any other encoding type, but I seem not able to get -1 or -40 for the starting value whichever encoding scheme I try.

In the documentation I saw an example in Java which uses the "toByteArray()" function, which seems to get the starting values (-1 or -40). Can anyone help me?

Answer 1

If I correctly understand your question, you can use Buffer to get file contents, then read the bytes from it into your array.

Java byte type is a signed 8-bit integer, the equivalent in Node.js Buffer is buf.readInt8().

So you can read the required amount of bytes from Buffer into your array using buf.readInt8()

Or just convert it into Int8Array:

new Int8Array(new Buffer([100, 200, 255, 1, 32]));