Declare TypedArray length

Suggestion

🔍 Search Terms

typedarray length tuple typed array

✅ Viability Checklist

My suggestion meets these guidelines:

• This wouldn't be a breaking change in existing TypeScript/JavaScript code
• This wouldn't change the runtime behavior of existing JavaScript code
• This could be implemented without emitting different JS based on the types of the expressions
• This isn't a runtime feature (e.g. library functionality, non-ECMAScript syntax with JavaScript output, new syntax sugar for JS, etc.)
• This feature would agree with the rest of TypeScript's Design Goals.

⭐ Suggestion

A way to declare a fixed length TypedArray similar to Tuples.

📃 Motivating Example

Consider a hypothetical vector library, similar glmatrix:

function addVector2(out: Float32Array, v1: Float32Array, v2: Float32Array) {
  out[0] = v1[0] + v2[0]
  out[1] = v1[1] + v2[1]
  return out
}

There's currently no way to type check that the arguments are indeed Vector2's and not some other Float32Arrays. This is possible with Tuple types though using regular arrays. Since TypedArrays are inherently fixed length even at runtime, it makes sense for there to be some way of declaring length. Even if this is just a minimum length, that would be a huge improvement since that guarantees out of bounds indexing safety.

💻 Use Cases

Many uses of TypedArrays in JS make assumptions about length. But the main one would probably be vectors, matrices, quarternions, etc.

まず、要求されている固定長 TypedArray の動作を、既存のタプル型および TypeScript の現在の TypedArray 宣言と比較します。ベクトルの例をどのように型チェックするかを定義し、最小長のみをサポートするのか、正確な長さもサポートするのかを含めて決定し、互換性のない TypedArray の長さが拒否されることを示すテストカバレッジを追加します。