Adds Array.prototype.at, String.prototype.at, and `TypedArray.pro…

…totype.at` polyfills

polyfills/Array/prototype/at/config.toml

@@ -0,0 +1,29 @@
+aliases = [ "es2022" ]
+dependencies = [
+	"_ESAbstract.CreateMethodProperty",
+	"_ESAbstract.Get",
+	"_ESAbstract.LengthOfArrayLike",
+	"_ESAbstract.ToIntegerOrInfinity",
+	"_ESAbstract.ToObject",
+	"_ESAbstract.ToString",
+]
+spec = "https://tc39.es/ecma262/#sec-array.prototype.at"
+docs = "https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/at"
+
+[browsers]
+android = "*"
+bb = "*"
+chrome = "< 92"
+edge = "*"
+edge_mob = "*"
+firefox = "< 90"
+firefox_mob = "< 90"
+ie = "*"
+ie_mob = "*"
+ios_chr = "*"
+ios_saf = "*"
+op_mini = "*"
+op_mob = "*"
+opera = "< 78"
+safari = "*"
+samsung_mob = "< 16"

polyfills/Array/prototype/at/detect.js

@@ -0,0 +1 @@
+'at' in Array.prototype

polyfills/Array/prototype/at/polyfill.js

@@ -0,0 +1,19 @@
+/* global CreateMethodProperty, Get, LengthOfArrayLike, ToIntegerOrInfinity, ToObject, ToString */
+// 23.1.3.1. Array.prototype.at ( index )
+CreateMethodProperty(Array.prototype, 'at', function at(index) {
+	// 1. Let O be ? ToObject(this value).
+	var O = ToObject(this);
+	// 2. Let len be ? LengthOfArrayLike(O).
+	var len = LengthOfArrayLike(O);
+	// 3. Let relativeIndex be ? ToIntegerOrInfinity(index).
+	var relativeIndex = ToIntegerOrInfinity(index);
+	// 4. If relativeIndex ≥ 0, then
+	// 4.a. Let k be relativeIndex.
+	// 5. Else,
+	// 5.a. Let k be len + relativeIndex.
+	var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+	// 6. If k < 0 or k ≥ len, return undefined.
+	if (k < 0 || k >= len) return undefined;
+	// 7. Return ? Get(O, ! ToString(𝔽(k))).
+	return Get(O, ToString(k));
+});

polyfills/Array/prototype/at/tests.js

@@ -0,0 +1,44 @@
+/* eslint-env mocha, browser */
+/* global proclaim */
+
+it('is a function', function () {
+	proclaim.isFunction(Array.prototype.at);
+});
+
+it('has correct arity', function () {
+	proclaim.arity(Array.prototype.at, 1);
+});
+
+it('has correct name', function () {
+	proclaim.hasName(Array.prototype.at, 'at');
+});
+
+it('is not enumerable', function () {
+	proclaim.isNotEnumerable(Array.prototype, 'at');
+});
+
+describe('at', function () {
+	it('retrieves values by index for arrays', function () {
+		var array = ['a', 'b', 'c'];
+		proclaim.equal(array.at(undefined), 'a');
+		proclaim.equal(array.at(-4), undefined);
+		proclaim.equal(array.at(-2), 'b');
+		proclaim.equal(array.at(-0.5), 'a');
+		proclaim.equal(array.at(0), 'a');
+		proclaim.equal(array.at(0.5), 'a');
+		proclaim.equal(array.at(2), 'c');
+		proclaim.equal(array.at(4), undefined);
+	});
+
+	it('retrieves values by index for array-like objects', function () {
+		var object = { 0: 'a', 1: 'b', 2: 'c', 3: 'd', length: 3 };
+		proclaim.equal(Array.prototype.at.call(object, undefined), 'a');
+		proclaim.equal(Array.prototype.at.call(object, -4), undefined);
+		proclaim.equal(Array.prototype.at.call(object, -2), 'b');
+		proclaim.equal(Array.prototype.at.call(object, -0.5), 'a');
+		proclaim.equal(Array.prototype.at.call(object, 0), 'a');
+		proclaim.equal(Array.prototype.at.call(object, 0.5), 'a');
+		proclaim.equal(Array.prototype.at.call(object, 2), 'c');
+		proclaim.equal(Array.prototype.at.call(object, 4), undefined);
+	});
+});

polyfills/String/prototype/at/config.toml

@@ -0,0 +1,27 @@
+aliases = [ "es2022" ]
+dependencies = [
+	"_ESAbstract.CreateMethodProperty",
+	"_ESAbstract.RequireObjectCoercible",
+	"_ESAbstract.ToIntegerOrInfinity",
+	"_ESAbstract.ToString",
+]
+spec = "https://tc39.es/ecma262/#sec-string.prototype.at"
+docs = "https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/at"
+
+[browsers]
+android = "*"
+bb = "*"
+chrome = "< 92"
+edge = "*"
+edge_mob = "*"
+firefox = "< 90"
+firefox_mob = "< 90"
+ie = "*"
+ie_mob = "*"
+ios_chr = "*"
+ios_saf = "*"
+op_mini = "*"
+op_mob = "*"
+opera = "< 78"
+safari = "*"
+samsung_mob = "< 16"

polyfills/String/prototype/at/detect.js

@@ -0,0 +1 @@
+'at' in String.prototype

polyfills/String/prototype/at/polyfill.js

@@ -0,0 +1,21 @@
+/* global CreateMethodProperty, RequireObjectCoercible, ToIntegerOrInfinity, ToString */
+// 22.1.3.1. String.prototype.at ( index )
+CreateMethodProperty(String.prototype, 'at', function at(index) {
+	// 1. Let O be ? RequireObjectCoercible(this value).
+	var O = RequireObjectCoercible(this);
+	// 2. Let S be ? ToString(O).
+	var S = ToString(O);
+	// 3. Let len be the length of S.
+	var len = S.length;
+	// 4. Let relativeIndex be ? ToIntegerOrInfinity(index).
+	var relativeIndex = ToIntegerOrInfinity(index);
+	// 5. If relativeIndex ≥ 0, then
+	// 5.a. Let k be relativeIndex.
+	// 6. Else,
+	// 6.a. Let k be len + relativeIndex.
+	var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+	// 7. If k < 0 or k ≥ len, return undefined.
+	if (k < 0 || k >= len) return undefined;
+	// 8. Return the substring of S from k to k + 1.
+	return S.substring(k, k + 1);
+});

polyfills/String/prototype/at/tests.js

@@ -0,0 +1,32 @@
+/* eslint-env mocha, browser */
+/* global proclaim */
+
+it('is a function', function () {
+	proclaim.isFunction(String.prototype.at);
+});
+
+it('has correct arity', function () {
+	proclaim.arity(String.prototype.at, 1);
+});
+
+it('has correct name', function () {
+	proclaim.hasName(String.prototype.at, 'at');
+});
+
+it('is not enumerable', function () {
+	proclaim.isNotEnumerable(String.prototype, 'at');
+});
+
+describe('at', function () {
+	it('retrieves values by index for strings', function () {
+		var string = 'abc';
+		proclaim.equal(string.at(undefined), 'a');
+		proclaim.equal(string.at(-4), undefined);
+		proclaim.equal(string.at(-2), 'b');
+		proclaim.equal(string.at(-0.5), 'a');
+		proclaim.equal(string.at(0), 'a');
+		proclaim.equal(string.at(0.5), 'a');
+		proclaim.equal(string.at(2), 'c');
+		proclaim.equal(string.at(4), undefined);
+	});
+});

polyfills/TypedArray/prototype/at/config.toml

@@ -0,0 +1,28 @@
+aliases = [ "es2022" ]
+dependencies = [
+	"_ESAbstract.CreateMethodProperty",
+	"_ESAbstract.Get",
+	"_ESAbstract.ToIntegerOrInfinity",
+	"_ESAbstract.ToString",
+	"ArrayBuffer",
+]
+spec = "https://tc39.es/ecma262/#sec-%typedarray%.prototype.at"
+docs = "https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray/at"
+
+[browsers]
+android = "*"
+bb = "*"
+chrome = "< 92"
+edge = "*"
+edge_mob = "*"
+firefox = "< 90"
+firefox_mob = "< 90"
+ie = "*"
+ie_mob = "*"
+ios_chr = "*"
+ios_saf = "*"
+op_mini = "*"
+op_mob = "*"
+opera = "< 78"
+safari = "*"
+samsung_mob = "< 16"

polyfills/TypedArray/prototype/at/detect.js

@@ -0,0 +1,2 @@
+// use "Int8Array" as a proxy for support of "TypedArray" subclasses
+'Int8Array' in self && 'at' in self.Int8Array.prototype

polyfills/TypedArray/prototype/at/polyfill.js

@@ -0,0 +1,38 @@
+/* global CreateMethodProperty, Get, ToIntegerOrInfinity, ToString */
+// 23.2.3.1. %TypedArray%.prototype.at ( index )
+(function () {
+	function at(index) {
+		// 1. Let O be the this value.
+		var O = this;
+		// 2. Perform ? ValidateTypedArray(O).
+		// TODO: Add ValidateTypedArray
+		// 3. Let len be O.[[ArrayLength]].
+		var len = O.length;
+		// 4. Let relativeIndex be ? ToIntegerOrInfinity(index).
+		var relativeIndex = ToIntegerOrInfinity(index);
+		// 5. If relativeIndex ≥ 0, then
+		// 5.a. Let k be relativeIndex.
+		// 6. Else,
+		// 6.a. Let k be len + relativeIndex.
+		var k = relativeIndex >= 0 ? relativeIndex : len + relativeIndex;
+		// 7. If k < 0 or k ≥ len, return undefined.
+		if (k < 0 || k >= len) return undefined;
+		// 8. Return ! Get(O, ! ToString(𝔽(k))).
+		return Get(O, ToString(k));
+	}
+
+	if ('__proto__' in self.Int8Array.prototype) {
+		// set this on the underlying "TypedArrayPrototype", which is shared with all "TypedArray" subclasses
+		CreateMethodProperty(self.Int8Array.prototype.__proto__, 'at', at);
+	} else {
+		CreateMethodProperty(self.Int8Array.prototype, 'at', at);
+		CreateMethodProperty(self.Uint8Array.prototype, 'at', at);
+		CreateMethodProperty(self.Uint8ClampedArray.prototype, 'at', at);
+		CreateMethodProperty(self.Int16Array.prototype, 'at', at);
+		CreateMethodProperty(self.Uint16Array.prototype, 'at', at);
+		CreateMethodProperty(self.Int32Array.prototype, 'at', at);
+		CreateMethodProperty(self.Uint32Array.prototype, 'at', at);
+		CreateMethodProperty(self.Float32Array.prototype, 'at', at);
+		CreateMethodProperty(self.Float64Array.prototype, 'at', at);
+	}
+})();

polyfills/TypedArray/prototype/at/tests.js

@@ -0,0 +1,63 @@
+/* eslint-env mocha, browser */
+/* global proclaim, Int8Array */
+
+// use "Int8Array" as a proxy for all "TypedArray" subclasses
+if ('Int8Array' in self) {
+	it('is a function', function () {
+		proclaim.isFunction(Int8Array.prototype.at);
+	});
+
+	it('has correct arity', function () {
+		proclaim.arity(Int8Array.prototype.at, 1);
+	});
+
+	it('has correct name', function () {
+		proclaim.hasName(Int8Array.prototype.at, 'at');
+	});
+
+	it('is not enumerable', function () {
+		if ('__proto__' in Int8Array.prototype) {
+			proclaim.isNotEnumerable(Int8Array.prototype.__proto__, 'at');
+		} else {
+			proclaim.isNotEnumerable(Int8Array.prototype, 'at');
+		}
+	});
+
+	describe('at', function () {
+		var supportsGetters = (function() {
+			try {
+				var a = {};
+				Object.defineProperty(a, "t", {
+					configurable: true,
+					enumerable: false,
+					get: function() {
+						return true;
+					},
+					set: undefined
+				});
+				return !!a.t;
+			} catch (e) {
+				return false;
+			}
+		})();
+
+		// `new Int8Array(length)` fails with "Getters & setters cannot be defined on this javascript engine" in IE8
+		// due to a bug in the `ArrayBuffer` polyfill: https://github.com/inexorabletash/polyfill/issues/23
+		if (supportsGetters) {
+			it('retrieves values by index for typed arrays', function () {
+				var typedArray = new Int8Array(3);
+				typedArray[0] = 1;
+				typedArray[1] = 2;
+				typedArray[2] = 3;
+				proclaim.equal(typedArray.at(undefined), 1);
+				proclaim.equal(typedArray.at(-4), undefined);
+				proclaim.equal(typedArray.at(-2), 2);
+				proclaim.equal(typedArray.at(-0.5), 1);
+				proclaim.equal(typedArray.at(0), 1);
+				proclaim.equal(typedArray.at(0.5), 1);
+				proclaim.equal(typedArray.at(2), 3);
+				proclaim.equal(typedArray.at(4), undefined);
+			});
+		}
+	});
+}

polyfills/_ESAbstract/LengthOfArrayLike/config.toml

@@ -0,0 +1,23 @@
+dependencies = [
+  "_ESAbstract.Get",
+  "_ESAbstract.ToLength",
+]
+spec = "https://tc39.github.io/ecma262/#sec-lengthofarraylike"
+
+[browsers]
+android = "*"
+bb = "*"
+chrome = "*"
+edge = "*"
+edge_mob = "*"
+firefox = "*"
+firefox_mob = "*"
+ie = "*"
+ie_mob = "*"
+ios_chr = "*"
+ios_saf = "*"
+op_mini = "*"
+op_mob = "*"
+opera = "*"
+safari = "*"
+samsung_mob = "*"

polyfills/_ESAbstract/LengthOfArrayLike/polyfill.js

@@ -0,0 +1,6 @@
+/* global Get, ToLength */
+// 7.3.19. LengthOfArrayLike ( obj )
+function LengthOfArrayLike(obj) { // eslint-disable-line no-unused-vars
+	// 1. Return ℝ(? ToLength(? Get(obj, "length"))).
+	return ToLength(Get(obj, 'length'));
+}

polyfills/_ESAbstract/ToIntegerOrInfinity/config.toml

@@ -0,0 +1,22 @@
+dependencies = [
+  "_ESAbstract.ToNumber",
+]
+spec = "https://tc39.github.io/ecma262/#sec-tointegerorinfinity"
+
+[browsers]
+android = "*"
+bb = "*"
+chrome = "*"
+edge = "*"
+edge_mob = "*"
+firefox = "*"
+firefox_mob = "*"
+ie = "*"
+ie_mob = "*"
+ios_chr = "*"
+ios_saf = "*"
+op_mini = "*"
+op_mob = "*"
+opera = "*"
+safari = "*"
+samsung_mob = "*"

polyfills/_ESAbstract/ToIntegerOrInfinity/polyfill.js

@@ -0,0 +1,18 @@
+/* global ToNumber */
+// 7.1.5. ToIntegerOrInfinity ( argument )
+function ToIntegerOrInfinity(argument) { // eslint-disable-line no-unused-vars
+	// 1. Let number be ? ToNumber(argument).
+	var number = ToNumber(argument);
+	// 2. If number is NaN, +0𝔽, or -0𝔽, return 0.
+	if (isNaN(number) || number === 0 || 1/number === -Infinity) return 0;
+	// 3. If number is +∞𝔽, return +∞.
+	if (number === Infinity) return Infinity;
+	// 4. If number is -∞𝔽, return -∞.
+	if (number === -Infinity) return -Infinity;
+	// 5. Let integer be floor(abs(ℝ(number))).
+	var integer = Math.floor(Math.abs(number));
+	// 6. If number < +0𝔽, set integer to -integer.
+	if (number < 0) integer = -integer;
+	// 7. Return integer.
+	return integer;
+}