Best practices

I am working on a byte editor like DataView but with more features and I was wondering how to detect if a TypedArray was signed or not.

I already have this,

const signedTypes = new Set([
    Int8Array,
    Int16Array,
    Int32Array,
    BigInt64Array
]);

function isSigned(TypedArray) {
    return signedTypes.has(TypedArray.constructor);
}

But this seems too manual - for example, if there was a new signed TypedArray like 20 years into the future I'm going to have to go back to my source code and add it into the list.

I could also check if the name matches Int or BigInt but that feels too hacky.

Feedback is appreciated, Thanks 🙏

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2 Replies 2

Pointy
•

Clearly if the array is of length 0 it doesn't matter. So if the length is at least 1, you can save the value at position 0, put -1 in it, then get the value back out. If the value you get is negative, it's a signed array; otherwise not.

function isSigned(typed) {
   if (!typed?.length) return false;
   const save = typed[0];
   typed[0] = -1;
   const rv = typed[0] < 0; // it's signed if this is true
   typed[0] = save;
   return rv;
}
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Shohjahon Jalilov
•

Thanks to Pointy I have found a good solution.

function isSigned(TypedArray) {
    const sample = TypedArray.BYTES_PER_ELEMENT === 8 ? [-1n] : [-1];
    const array = new TypedArray(sample);
    return ArrayBuffer.isView(array) && array[0] < 0;
}
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