Optimizing your use of fromCharCode.apply with Uint8Array in TypeScript 3

I recently came across some code that I inherited which appears like this: 


String.fromCharCode.apply(null, new Uint8Array(license));
Recently, we updated our project dependencies to TypeScript 3, which raised an error stating: 

Argument of type 'Uint8Array' is not assignable to parameter of type 'number[]'.
  Type 'Uint8Array' is missing the following properties from type 'number[]': pop, push, concat, shift, and 3 more.
I noticed similar issues in other parts of the code, all related to Uint8Array except for one instance that involved a Uint16Array. It seems the problem stems from changes in the Uint8Array constructor, which has multiple overloads. I attempted to modify the code like so: 

const jsonKey: string = String.fromCharCode.apply(null, Array.from(new Uint8Array(license)));
and 

const jsonKey: string = String.fromCharCode.apply(null, Array.prototype.slice.call(new Uint8Array(license)));
Unfortunately, neither of these solutions successfully replicated the original functionality of the code, although they did suppress the error messages.

typescriptecmascript-6uint8array

Answer №1

If you aim for better readability over compactness, consider the following approach:

let jsonKey: string = "";
(new Uint8Array(license)).forEach(function (byte: number) {
    jsonKey += String.fromCharCode(byte);
});

Answer №2

It seems like you were so close with your initial try; all you have to do is make sure to clearly define the generic parameter:

String.fromCharCode.apply(null, Array.from<number>(new Uint8Array(license)));

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