|
1 | | -# template-for-proposals |
2 | | - |
3 | | -A repository template for ECMAScript proposals. |
4 | | - |
5 | | -## Before creating a proposal |
6 | | - |
7 | | -Please ensure the following: |
8 | | - 1. You have read the [process document](https://tc39.github.io/process-document/) |
9 | | - 1. You have reviewed the [existing proposals](https://github.com/tc39/proposals/) |
10 | | - 1. You are aware that your proposal requires being a member of TC39, or locating a TC39 delegate to "champion" your proposal |
11 | | - |
12 | | -## Create your proposal repo |
13 | | - |
14 | | -Follow these steps: |
15 | | - 1. Click the green ["use this template"](https://github.com/tc39/template-for-proposals/generate) button in the repo header. (Note: Do not fork this repo in GitHub's web interface, as that will later prevent transfer into the TC39 organization) |
16 | | - 1. Go to your repo settings “Options” page, under “GitHub Pages”, and set the source to the **main branch** under the root (and click Save, if it does not autosave this setting) |
17 | | - 1. check "Enforce HTTPS" |
18 | | - 1. On "Options", under "Features", Ensure "Issues" is checked, and disable "Wiki", and "Projects" (unless you intend to use Projects) |
19 | | - 1. Under "Merge button", check "automatically delete head branches" |
20 | | -<!-- |
21 | | - 1. Avoid merge conflicts with build process output files by running: |
22 | | - ```sh |
23 | | - git config --local --add merge.output.driver true |
24 | | - git config --local --add merge.output.driver true |
25 | | - ``` |
26 | | - 1. Add a post-rewrite git hook to auto-rebuild the output on every commit: |
27 | | - ```sh |
28 | | - cp hooks/post-rewrite .git/hooks/post-rewrite |
29 | | - chmod +x .git/hooks/post-rewrite |
30 | | - ``` |
31 | | ---> |
32 | | - 1. ["How to write a good explainer"][explainer] explains how to make a good first impression. |
33 | | - |
34 | | - > Each TC39 proposal should have a `README.md` file which explains the purpose |
35 | | - > of the proposal and its shape at a high level. |
36 | | - > |
37 | | - > ... |
38 | | - > |
39 | | - > The rest of this page can be used as a template ... |
40 | | -
|
41 | | - Your explainer can point readers to the `index.html` generated from `spec.emu` |
42 | | - via markdown like |
43 | | - |
44 | | - ```markdown |
45 | | - You can browse the [ecmarkup output](https://ACCOUNT.github.io/PROJECT/) |
46 | | - or browse the [source](https://github.com/ACCOUNT/PROJECT/blob/HEAD/spec.emu). |
47 | | - ``` |
48 | | - |
49 | | - where *ACCOUNT* and *PROJECT* are the first two path elements in your project's Github URL. |
50 | | - For example, for github.com/**tc39**/**template-for-proposals**, *ACCOUNT* is "tc39" |
51 | | - and *PROJECT* is "template-for-proposals". |
52 | | - |
53 | | - |
54 | | -## Maintain your proposal repo |
55 | | - |
56 | | - 1. Make your changes to `spec.emu` (ecmarkup uses HTML syntax, but is not HTML, so I strongly suggest not naming it ".html") |
57 | | - 1. Any commit that makes meaningful changes to the spec, should run `npm run build` and commit the resulting output. |
58 | | - 1. Whenever you update `ecmarkup`, run `npm run build` and commit any changes that come from that dependency. |
59 | | - |
60 | | - [explainer]: https://github.com/tc39/how-we-work/blob/HEAD/explainer.md |
| 1 | +# proposal-arraybuffer-equals |
| 2 | + |
| 3 | +This is a proposal to add a new method, `equals(b: ArrayBuffer)`, to JavaScript's `ArrayBuffer` class. It has not yet been presented to the JavaScript standards committee. |
| 4 | + |
| 5 | +## The problem |
| 6 | + |
| 7 | +```typescript |
| 8 | +const encoder = new TextEncoder(); |
| 9 | +const input = 'sample'; |
| 10 | +const a = encoder.encode(input); |
| 11 | +const b = encoder.encode(input); |
| 12 | +console.log(a === b); // returns false |
| 13 | +console.log(a == b); // returns false |
| 14 | +``` |
| 15 | + |
| 16 | +The re-definition [Abstract Equality Comparison](https://tc39.es/ecma262/#sec-abstract-equality-comparison) or [Strict Equality Comparison](https://tc39.es/ecma262/#sec-strict-equality-comparison) is break change behavior. |
| 17 | + |
| 18 | +So we need to **define a new method**, |
| 19 | + |
| 20 | +## How compare two ArrayBuffer object is equality |
| 21 | + |
| 22 | +To solve this problem, you need to define a method. |
| 23 | + |
| 24 | +```typescript |
| 25 | +// The is TypeScript code |
| 26 | +function isEquals(a: ArrayBuffer, b: ArrayBuffer) { |
| 27 | + if (!(a instanceof ArrayBuffer)) { |
| 28 | + throw new TypeError(); |
| 29 | + } else if (!(b instanceof ArrayBuffer)) { |
| 30 | + throw new TypeError(); |
| 31 | + } else if (a === b) { |
| 32 | + return true; |
| 33 | + } else if (a.byteLength !== b.byteLength) { |
| 34 | + return false; |
| 35 | + } |
| 36 | + const view1 = new DataView(a); |
| 37 | + const view2 = new DataView(b); |
| 38 | + for (let i = 0; i < view1.byteLength; i++) { |
| 39 | + if (view1.getUint8(i) !== view2.getUint8(i)) { |
| 40 | + return false; |
| 41 | + } |
| 42 | + } |
| 43 | + return true; |
| 44 | +} |
| 45 | +``` |
| 46 | + |
| 47 | +## `ArrayBuffer.isEquals` |
| 48 | + |
| 49 | +To do this, we propose a new method, `ArrayBuffer.isEquals(a, b)`, which compare two array buffer is equality (bit-wise) |
| 50 | + |
| 51 | +```typescript |
| 52 | +// returns false |
| 53 | +ArrayBuffer.isEquals(Uint8Array.of(0), undefined); |
| 54 | +// returns false |
| 55 | +ArrayBuffer.isEquals(Uint8Array.of(0), null); |
| 56 | +// returns false |
| 57 | +ArrayBuffer.isEquals(Uint8Array.of(0), Uint8Array.of(0, 1)); |
| 58 | +// returns true |
| 59 | +ArrayBuffer.isEquals(Uint8Array.of(0), Uint8Array.of(0)); |
| 60 | +// returns true |
| 61 | +ArrayBuffer.isEquals( |
| 62 | + Uint32Array.from([Number.MAX_SAFE_INTEGER]).buffer, |
| 63 | + Uint8Array.of(255, 255, 255, 255).buffer, |
| 64 | +); |
| 65 | +``` |
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