Add relative indexing method proposal

CHANGELOG.md

@@ -1,5 +1,8 @@
 ## Changelog
 ##### Unreleased
+- Added [relative indexing method stage 3 proposal](https://github.com/tc39/proposal-relative-indexing-method)
+  - `Array#at`
+  - `%TypedArray%#at`
 - Added [`Number.range` stage 1 proposal](https://github.com/tc39/proposal-Number.range)
   - `Number.range`
   - `BigInt.range`
@@ -8,6 +11,7 @@
   - `%TypedArray%#filterOut`
 - Added [array deduplication stage 1 proposal](https://github.com/tc39/proposal-array-unique)
   - `Array#uniqueBy`
+- Added code points / code units explicit feature detection in `String#at` for preventing breakage code which use obsolete `String#at` proposal polyfill
 - Added the missed `(es|stable)/instance/replace-all` entries
 - Updated compat data mapping for Opera - from Opera 69, the difference with Chrome versions increased to 14
 - Compat data mapping for modern Android WebView to Chrome moved from targets parser directly to compat data

README.md

@@ -1778,7 +1778,40 @@ Promise.any([
 core-js(-pure)/stage/3
 ```
 
-None.
+##### [Relative indexing method](https://github.com/tc39/proposal-relative-indexing-method)[⬆](#index)
+Modules [`esnext.array.at`](https://github.com/zloirock/core-js/blob/v3.7.0/packages/core-js/modules/esnext.array.at.js) and [`esnext.typed-array.at`](https://github.com/zloirock/core-js/blob/v3.7.0/packages/core-js/modules/esnext.typed-array.at.js)
+> **Warning! Because of the conflict with [another proposal](#stringat), this method is not available on `String.prototype` in this version.**
+
+```js
+class Array {
+  at(index: int): any;
+}
+
+class [
+  Int8Array,
+  Uint8Array,
+  Uint8ClampedArray,
+  Int16Array,
+  Uint16Array,
+  Int32Array,
+  Uint32Array,
+  Float32Array,
+  Float64Array,
+] {
+  at(index: int): any;
+}
+```
+[*CommonJS entry points:*](#commonjs-api)
+```
+core-js/proposals/relative-indexing-method
+core-js(-pure)/features/array/at
+core-js(-pure)/features/typed-array/at
+```
+[*Examples*](http://es6.zloirock.ru/#log(%5B1%2C%202%2C%203%5D.at(1))%3B%20%20%2F%2F%20%3D%3E%202%0Alog(%5B1%2C%202%2C%203%5D.at(-1))%3B%20%2F%2F%20%3D%3E%203):
+```js
+[1, 2, 3].at(1);  // => 2
+[1, 2, 3].at(-1); // => 3
+```
 
 #### Stage 2 proposals[⬆](#index)
 [*CommonJS entry points:*](#commonjs-api)

packages/core-js-compat/src/data.js

@@ -1258,6 +1258,8 @@ const data = {
   },
   'esnext.array.is-template-object': {
   },
+  'esnext.array.at': {
+  },
   'esnext.array.last-index': {
   },
   'esnext.array.last-item': {
@@ -1492,6 +1494,8 @@ const data = {
   // TODO: Remove from `core-js@4`
   'esnext.symbol.replace-all': {
   },
+  'esnext.typed-array.at': {
+  },
   'esnext.typed-array.filter-out': {
   },
   'esnext.weak-map.delete-all': {

packages/core-js-compat/src/modules-by-versions.js

@@ -65,10 +65,12 @@ module.exports = {
     'esnext.weak-map.emplace',
   ],
   3.8: [
+    'esnext.array.at',
     'esnext.array.filter-out',
     'esnext.array.unique-by',
     'esnext.bigint.range',
     'esnext.number.range',
+    'esnext.typed-array.at',
     'esnext.typed-array.filter-out',
   ],
 };

packages/core-js-pure/override/modules/esnext.typed-array.at.js

@@ -0,0 +1 @@
+// empty

packages/core-js/features/array/at.js

@@ -0,0 +1,4 @@
+require('../../modules/esnext.array.at');
+var entryUnbind = require('../../internals/entry-unbind');
+
+module.exports = entryUnbind('Array', 'at');

packages/core-js/features/array/index.js

@@ -1,5 +1,6 @@
 var parent = require('../../es/array');
 require('../../modules/es.map');
+require('../../modules/esnext.array.at');
 require('../../modules/esnext.array.filter-out');
 require('../../modules/esnext.array.is-template-object');
 require('../../modules/esnext.array.last-item');

packages/core-js/features/array/virtual/at.js

@@ -0,0 +1,4 @@
+require('../../../modules/esnext.array.at');
+var entryVirtual = require('../../../internals/entry-virtual');
+
+module.exports = entryVirtual('Array').at;

packages/core-js/features/array/virtual/index.js

@@ -1,4 +1,6 @@
 var parent = require('../../../es/array/virtual');
+require('../../../modules/esnext.array.at');
 require('../../../modules/esnext.array.filter-out');
+require('../../../modules/esnext.array.unique-by');
 
 module.exports = parent;

packages/core-js/features/instance/at.js

@@ -1,9 +1,13 @@
-var at = require('../string/virtual/at');
+var arrayAt = require('../array/virtual/at');
+var stringAt = require('../string/virtual/at');
 
+var ArrayPrototype = Array.prototype;
 var StringPrototype = String.prototype;
 
 module.exports = function (it) {
   var own = it.at;
-  return typeof it === 'string' || it === StringPrototype
-    || (it instanceof String && own === StringPrototype.at) ? at : own;
+  if (it === ArrayPrototype || (it instanceof Array && own === ArrayPrototype.at)) return arrayAt;
+  if (typeof it === 'string' || it === StringPrototype || (it instanceof String && own === StringPrototype.at)) {
+    return stringAt;
+  } return own;
 };

packages/core-js/features/string/index.js

@@ -1,5 +1,7 @@
 var parent = require('../../es/string');
 require('../../modules/esnext.string.at');
+// TODO: disabled by default because of the conflict with another proposal
+// require('../../modules/esnext.string.at-alternative');
 require('../../modules/esnext.string.code-points');
 // TODO: remove from `core-js@4`
 require('../../modules/esnext.string.match-all');

packages/core-js/features/string/virtual/index.js

@@ -1,5 +1,7 @@
 var parent = require('../../../es/string/virtual');
 require('../../../modules/esnext.string.at');
+// TODO: disabled by default because of the conflict with another proposal
+// require('../../../modules/esnext.string.at-alternative');
 require('../../../modules/esnext.string.code-points');
 // TODO: remove from `core-js@4`
 require('../../../modules/esnext.string.match-all');

packages/core-js/features/typed-array/at.js

@@ -0,0 +1 @@
+require('../../modules/esnext.typed-array.at');

packages/core-js/features/typed-array/index.js

@@ -1,4 +1,5 @@
 var parent = require('../../es/typed-array');
+require('../../modules/esnext.typed-array.at');
 require('../../modules/esnext.typed-array.filter-out');
 
 module.exports = parent;

packages/core-js/modules/esnext.array.at.js

@@ -0,0 +1,20 @@
+'use strict';
+var $ = require('../internals/export');
+var toObject = require('../internals/to-object');
+var toLength = require('../internals/to-length');
+var toInteger = require('../internals/to-integer');
+var addToUnscopables = require('../internals/add-to-unscopables');
+
+// `Array.prototype.at` method
+// https://github.com/tc39/proposal-relative-indexing-method
+$({ target: 'Array', proto: true }, {
+  at: function at(index) {
+    var O = toObject(this);
+    var len = toLength(O.length);
+    var relativeIndex = toInteger(index);
+    var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+    return (k < 0 || k >= len) ? undefined : O[k];
+  }
+});
+
+addToUnscopables('at');

packages/core-js/modules/esnext.string.at-alternative.js

@@ -0,0 +1,23 @@
+// TODO: disabled by default because of the conflict with another proposal
+'use strict';
+var $ = require('../internals/export');
+var requireObjectCoercible = require('../internals/require-object-coercible');
+var toLength = require('../internals/to-length');
+var toInteger = require('../internals/to-integer');
+var fails = require('../internals/fails');
+
+var FORCED = fails(function () {
+  return '𠮷'.at(0) !== '\uD842';
+});
+
+// `String.prototype.at` method
+// https://github.com/tc39/proposal-relative-indexing-method
+$({ target: 'String', proto: true, forced: FORCED }, {
+  at: function at(index) {
+    var S = String(requireObjectCoercible(this));
+    var len = toLength(S.length);
+    var relativeIndex = toInteger(index);
+    var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+    return (k < 0 || k >= len) ? undefined : S.charAt(k);
+  }
+});

packages/core-js/modules/esnext.string.at.js

@@ -1,10 +1,15 @@
 'use strict';
 var $ = require('../internals/export');
 var charAt = require('../internals/string-multibyte').charAt;
+var fails = require('../internals/fails');
+
+var FORCED = fails(function () {
+  return '𠮷'.at(0) !== '𠮷';
+});
 
 // `String.prototype.at` method
 // https://github.com/mathiasbynens/String.prototype.at
-$({ target: 'String', proto: true }, {
+$({ target: 'String', proto: true, forced: FORCED }, {
   at: function at(pos) {
     return charAt(this, pos);
   }

packages/core-js/modules/esnext.typed-array.at.js

@@ -0,0 +1,17 @@
+'use strict';
+var ArrayBufferViewCore = require('../internals/array-buffer-view-core');
+var toLength = require('../internals/to-length');
+var toInteger = require('../internals/to-integer');
+
+var aTypedArray = ArrayBufferViewCore.aTypedArray;
+var exportTypedArrayMethod = ArrayBufferViewCore.exportTypedArrayMethod;
+
+// `%TypedArray%.prototype.at` method
+// https://github.com/tc39/proposal-relative-indexing-method
+exportTypedArrayMethod('at', function at(index) {
+  var O = aTypedArray(this);
+  var len = toLength(O.length);
+  var relativeIndex = toInteger(index);
+  var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+  return (k < 0 || k >= len) ? undefined : O[k];
+});

packages/core-js/proposals/relative-indexing-method.js

@@ -0,0 +1,5 @@
+// https://github.com/tc39/proposal-relative-indexing-method
+require('../modules/esnext.array.at');
+// TODO: disabled by default because of the conflict with another proposal
+// require('../modules/esnext.string.at-alternative');
+require('../modules/esnext.typed-array.at');

packages/core-js/stage/3.js

@@ -1,3 +1,4 @@
+require('../proposals/relative-indexing-method');
 var parent = require('./4');
 
 module.exports = parent;

tests/commonjs.js

@@ -62,6 +62,7 @@ for (const _PATH of ['../packages/core-js-pure', '../packages/core-js']) {
   ok(typeof load('features/array/is-template-object') === 'function');
   ok(Array.isArray(load('features/array/from')('qwe')));
   ok(Array.isArray(load('features/array/of')('q', 'w', 'e')));
+  ok(load('features/array/at')([1, 2, 3], -2) === 2);
   ok(load('features/array/join')('qwe', 1) === 'q1w1e');
   ok(load('features/array/slice')('qwe', 1)[1] === 'e');
   ok(load('features/array/sort')([1, 3, 2])[1] === 2);
@@ -92,6 +93,7 @@ for (const _PATH of ['../packages/core-js-pure', '../packages/core-js']) {
   ok(load('features/array/includes')([1, 2, 3], 2));
   ok('next' in load('features/array/iterator')([]));
   ok(typeof load('features/array/unique-by') === 'function');
+  ok(load('features/array/virtual/at').call([1, 2, 3], -2) === 2);
   ok(load('features/array/virtual/join').call('qwe', 1) === 'q1w1e');
   ok(load('features/array/virtual/slice').call('qwe', 1)[1] === 'e');
   ok(load('features/array/virtual/splice').call([1, 2, 3], 1, 2)[0] === 2);
@@ -210,6 +212,7 @@ for (const _PATH of ['../packages/core-js-pure', '../packages/core-js']) {
   ok(load('features/string/code-point-at')('a', 0) === 97);
   ok(load('features/string/ends-with')('qwe', 'we'));
   ok(load('features/string/includes')('qwe', 'w'));
+  // ok(load('features/string/at-alternative')('123', -2) === '2');
   ok(load('features/string/repeat')('q', 3) === 'qqq');
   ok(load('features/string/starts-with')('qwe', 'qw'));
   ok(typeof load('features/string/anchor') === 'function');
@@ -239,6 +242,7 @@ for (const _PATH of ['../packages/core-js-pure', '../packages/core-js']) {
   ok(load('features/string/virtual/code-point-at').call('a', 0) === 97);
   ok(load('features/string/virtual/ends-with').call('qwe', 'we'));
   ok(load('features/string/virtual/includes').call('qwe', 'w'));
+  // ok(load('features/string/virtual/at-alternative').call('123', -2) === '2');
   ok(load('features/string/virtual/repeat').call('q', 3) === 'qqq');
   ok(load('features/string/virtual/starts-with').call('qwe', 'qw'));
   ok(typeof load('features/string/virtual/anchor') === 'function');
@@ -977,6 +981,7 @@ for (const _PATH of ['../packages/core-js-pure', '../packages/core-js']) {
   load('proposals/promise-any');
   load('proposals/promise-try');
   load('proposals/reflect-metadata');
+  load('proposals/relative-indexing-method');
   load('proposals/keys-composition');
   load('proposals/seeded-random');
   load('proposals/set-methods');
@@ -999,8 +1004,10 @@ for (const _PATH of ['../packages/core-js-pure', '../packages/core-js']) {
   const instanceAt = load('features/instance/at');
   ok(typeof instanceAt === 'function');
   ok(instanceAt({}) === undefined);
+  ok(typeof instanceAt([]) === 'function');
   ok(typeof instanceAt('') === 'function');
-  ok(instanceAt('').call('abc', 1) === 'b');
+  ok(instanceAt([]).call([1, 2, 3], 2) === 3);
+  ok(instanceAt('').call('123', 2) === '3');
 
   let instanceBind = load('features/instance/bind');
   ok(typeof instanceBind === 'function');
@@ -1653,6 +1660,7 @@ ok(typeof load('features/typed-array/int32-array') === 'function');
 ok(typeof load('features/typed-array/uint32-array') === 'function');
 ok(typeof load('features/typed-array/float32-array') === 'function');
 ok(typeof load('features/typed-array/float64-array') === 'function');
+load('features/typed-array/at');
 load('features/typed-array/copy-within');
 load('features/typed-array/entries');
 load('features/typed-array/every');

tests/compat/tests.js

@@ -1100,6 +1100,9 @@ GLOBAL.tests = {
       && set.add({}) == set
       && set[Symbol.toStringTag];
   }],
+  'esnext.array.at': function () {
+    return [].at;
+  },
   'esnext.array.filter-out': function () {
     return [].filterOut;
   },
@@ -1422,7 +1425,7 @@ GLOBAL.tests = {
     return Set.prototype.union;
   },
   'esnext.string.at': function () {
-    return String.prototype.at;
+    return '𠮷'.at(0) === '𠮷';
   },
   'esnext.string.code-points': function () {
     return String.prototype.codePoints;
@@ -1440,6 +1443,9 @@ GLOBAL.tests = {
   'esnext.symbol.replace-all': function () {
     return Symbol.replaceAll;
   },
+  'esnext.typed-array.at': function () {
+    return Int8Array.prototype.at;
+  },
   'esnext.typed-array.filter-out': function () {
     return Int8Array.prototype.filterOut;
   },

tests/pure/esnext.array.at.js

@@ -0,0 +1,27 @@
+import { STRICT } from '../helpers/constants';
+
+import at from 'core-js-pure/features/array/at';
+
+QUnit.test('Array#at', assert => {
+  assert.isFunction(at);
+  assert.same(1, at([1, 2, 3], 0));
+  assert.same(2, at([1, 2, 3], 1));
+  assert.same(3, at([1, 2, 3], 2));
+  assert.same(undefined, at([1, 2, 3], 3));
+  assert.same(3, at([1, 2, 3], -1));
+  assert.same(2, at([1, 2, 3], -2));
+  assert.same(1, at([1, 2, 3], -3));
+  assert.same(undefined, at([1, 2, 3], -4));
+  assert.same(1, at([1, 2, 3], 0.4));
+  assert.same(1, at([1, 2, 3], 0.5));
+  assert.same(1, at([1, 2, 3], 0.6));
+  assert.same(1, at([1], NaN));
+  assert.same(1, at([1]));
+  assert.same(1, at([1, 2, 3], -0));
+  assert.same(undefined, at(Array(1), 0));
+  assert.same(1, at({ 0: 1, length: 1 }, 0));
+  if (STRICT) {
+    assert.throws(() => at(null, 0), TypeError);
+    assert.throws(() => at(undefined, 0), TypeError);
+  }
+});

tests/pure/esnext.string.at-alternative.js

@@ -0,0 +1,28 @@
+// TODO: disabled by default because of the conflict with another proposal
+import { STRICT } from '../helpers/constants';
+
+import at from 'core-js-pure/features/string/at';
+
+QUnit.test('String#at', assert => {
+  assert.isFunction(at);
+  assert.same('1', at('123', 0));
+  assert.same('2', at('123', 1));
+  assert.same('3', at('123', 2));
+  assert.same(undefined, at('123', 3));
+  assert.same('3', at('123', -1));
+  assert.same('2', at('123', -2));
+  assert.same('1', at('123', -3));
+  assert.same(undefined, at('123', -4));
+  assert.same('1', at('123', 0.4));
+  assert.same('1', at('123', 0.5));
+  assert.same('1', at('123', 0.6));
+  assert.same('1', at('1', NaN));
+  assert.same('1', at('1'));
+  assert.same('1', at('123', -0));
+  assert.same('\uD842', at('𠮷'));
+  assert.same('1', at({ toString() { return '123'; } }, 0));
+  if (STRICT) {
+    assert.throws(() => at(null, 0), TypeError);
+    assert.throws(() => at(undefined, 0), TypeError);
+  }
+});