kiwix-js-pwa/www/js/lib/arrayFromPolyfill.js

/* globals
	IsCallable, GetMethod, Symbol, IsConstructor, Construct, ArrayCreate, GetIterator, IteratorClose,
	ToString, IteratorStep, IteratorValue, Call, CreateDataPropertyOrThrow, ToObject, ToLength, Get, CreateMethodProperty
*/
(function () {
    // Detection
    if ('from' in Array && (function () {
        try {
            Array.from({ length: -Infinity });
    
            if (Array.from(new self.Set(['a']))[0] !== 'a') {
                return false;
            }
    
            if (Array.from(new self.Map([['a', 'one']]))[0][0] !== 'a') {
                return false;
            }
    
            return true;
        } catch (e) {
            return false;
        }
    }())) { return; }

	var toString = Object.prototype.toString;
	var stringMatch = String.prototype.match;
	// A cross-realm friendly way to detect if a value is a String object or literal.
	function isString(value) {
		if (typeof value === 'string') { return true; }
		if (typeof value !== 'object') { return false; }
		return toString.call(value) === '[object String]';
	}

	// 22.1.2.1. Array.from ( items [ , mapfn [ , thisArg ] ] )
	CreateMethodProperty(Array, 'from', function from(items /* [ , mapfn [ , thisArg ] ] */) { // eslint-disable-line no-undef
		// 1. Let C be the this value.
		var C = this;
		// 2. If mapfn is undefined, let mapping be false.
		var mapfn = arguments.length > 1 ? arguments[1] : undefined;
		if (mapfn === undefined) {
			var mapping = false;
			// 3. Else,
		} else {
			// a. If IsCallable(mapfn) is false, throw a TypeError exception.
			if (IsCallable(mapfn) === false) {
				throw new TypeError(Object.prototype.toString.call(mapfn) + ' is not a function.');
			}
			// b. If thisArg is present, let T be thisArg; else let T be undefined.
			var thisArg = arguments.length > 2 ? arguments[2] : undefined;
			if (thisArg !== undefined) {
				var T = thisArg;
			} else {
				T = undefined;
			}
			// c. Let mapping be true.
			mapping = true;

		}
		// 4. Let usingIterator be ? GetMethod(items, @@iterator).
		var usingIterator = GetMethod(items, Symbol.iterator);
		// 5. If usingIterator is not undefined, then
		if (usingIterator !== undefined) {
			// a. If IsConstructor(C) is true, then
			if (IsConstructor(C)) {
				// i. Let A be ? Construct(C).
				var A = Construct(C);
				// b. Else,
			} else {
				// i. Let A be ! ArrayCreate(0).
				A = ArrayCreate(0);
			}
			// c. Let iteratorRecord be ? GetIterator(items, usingIterator).
			var iteratorRecord = GetIterator(items, usingIterator);
			// d. Let k be 0.
			var k = 0;
			// e. Repeat,
			// eslint-disable-next-line no-constant-condition
			while (true) {
				// i. If k ≥ 2^53-1, then
				if (k >= (Math.pow(2, 53) - 1)) {
					// 1. Let error be Completion{[[Type]]: throw, [[Value]]: a newly created TypeError object, [[Target]]: empty}.
					var error = new TypeError('Iteration count can not be greater than or equal 9007199254740991.');
					// 2. Return ? IteratorClose(iteratorRecord, error).
					return IteratorClose(iteratorRecord, error);
				}
				// ii. Let Pk be ! ToString(k).
				var Pk = ToString(k);
				// iii. Let next be ? IteratorStep(iteratorRecord).
				var next = IteratorStep(iteratorRecord);
				// iv. If next is false, then
				if (next === false) {
					// 1. Perform ? Set(A, "length", k, true).
					A.length = k;
					// 2. Return A.
					return A;
				}
				// v. Let nextValue be ? IteratorValue(next).
				var nextValue = IteratorValue(next);
				// vi. If mapping is true, then
				if (mapping) {
					try {
						// Polyfill.io - The try catch accounts for step 2.
						// 1. Let mappedValue be Call(mapfn, T, « nextValue, k »).
						var mappedValue = Call(mapfn, T, [nextValue, k]);
						// 2. If mappedValue is an abrupt completion, return ? IteratorClose(iteratorRecord, mappedValue).
						// 3. Let mappedValue be mappedValue.[[Value]].
					} catch (e) {
						return IteratorClose(iteratorRecord, e);
					}

					// vii. Else, let mappedValue be nextValue.
				} else {
					mappedValue = nextValue;
				}
				try {
					// Polyfill.io - The try catch accounts for step ix.
					// viii. Let defineStatus be CreateDataPropertyOrThrow(A, Pk, mappedValue).
					CreateDataPropertyOrThrow(A, Pk, mappedValue);
					// ix. If defineStatus is an abrupt completion, return ? IteratorClose(iteratorRecord, defineStatus).
				} catch (e) {
					return IteratorClose(iteratorRecord, e);
				}
				// x. Increase k by 1.
				k = k + 1;
			}
		}
		// 6. NOTE: items is not an Iterable so assume it is an array-like object.
		// 7. Let arrayLike be ! ToObject(items).
		// Polyfill.io - For Strings we need to split astral symbols into surrogate pairs.
		if (isString(items)) {
			var arrayLike = stringMatch.call(items, /[\uD800-\uDBFF][\uDC00-\uDFFF]?|[^\uD800-\uDFFF]|./g) || [];
		} else {
			arrayLike = ToObject(items);
		}
		// 8. Let len be ? ToLength(? Get(arrayLike, "length")).
		var len = ToLength(Get(arrayLike, "length"));
		// 9. If IsConstructor(C) is true, then
		if (IsConstructor(C)) {
			// a. Let A be ? Construct(C, « len »).
			A = Construct(C, [len]);
			// 10. Else,
		} else {
			// a. Let A be ? ArrayCreate(len).
			A = ArrayCreate(len);
		}
		// 11. Let k be 0.
		k = 0;
		// 12. Repeat, while k < len
		while (k < len) {
			// a. Let Pk be ! ToString(k).
			Pk = ToString(k);
			// b. Let kValue be ? Get(arrayLike, Pk).
			var kValue = Get(arrayLike, Pk);
			// c. If mapping is true, then
			if (mapping === true) {
				// i. Let mappedValue be ? Call(mapfn, T, « kValue, k »).
				mappedValue = Call(mapfn, T, [kValue, k]);
				// d. Else, let mappedValue be kValue.
			} else {
				mappedValue = kValue;
			}
			// e. Perform ? CreateDataPropertyOrThrow(A, Pk, mappedValue).
			CreateDataPropertyOrThrow(A, Pk, mappedValue);
			// f. Increase k by 1.
			k = k + 1;
		}
		// 13. Perform ? Set(A, "length", len, true).
		A.length = len;
		// 14. Return A.
		return A;
	});
}());