在 Javascript 中继承 Uint8Array

Question

I try to use Uint8Array to simulate a byte[] or uint8[].

TypedArray.subarray creating a new view on the existing buffer,changes to the new object's contents will impact the original object and vice versa.

I always use it like this:

 let u = new Uint8Array(8) //'u' is 8 bytes let a = u.subarray(4) //'a' is 4 bytes console.log(a) // show [0,0,0,0], it is ok

but when I try to subclassing Uint8Array, subarray goes strange.

 class bytes extends Uint8Array { constructor(arg) { super(arg) } } let b = new bytes(8) //'b' is 8 bytes let c = b.subarray(4) //'c' should be 4 bytes, but is 8 bytes console.log(c) // show [0,0,0,0,0,0,0,0], ??????

I want to know what happened and how to fix it.

Answer 1

It has to do with how arguments are interpreted by the overloaded constructor.

This works correctly:

 class bytes extends Uint8Array { constructor(...args) { super(...args); } } let b = new bytes(8); let c = b.subarray(4); console.log(c);