polyfill-service/polyfills/Array/prototype/copyWithin/polyfill.js

A polyfill combinator

(function () {

	function hasProperty(o, p) {
    while (o) {
			if (Object.prototype.hasOwnProperty.call(o, p)) {
				return true;
			}
			if (typeof o !== 'object') {
				return false;
			}
      o = Object.getPrototypeOf(o);
    }
    return false;
  }

	function toInteger(n) {
		n = Number(n);
		if (isNaN(n)) {
			return 0;
		}
		if (n === 0 || n === Infinity || n === -Infinity) {
			return n;
		} else {
			return ((n < 0) ? -1 : 1) * Math.floor(Math.abs(n));
		}
	}

	Object.defineProperty(Array.prototype, 'copyWithin', {
		configurable: true,
		enumerable: false,
		writable: true,
		// 22.1.3.3 Array.prototype.copyWithin ( target, start [ , end ] )
		value: function (target, start/*, end*/) {
			var end = arguments[2];

			// 22.1.3.3.1 Let O be ? ToObject(this value).
			if (this === null || this === undefined) {
				throw new TypeError('Cannot call method on ' + this);
			}

			var o = Object(this);

			// 22.1.3.3.2 Let len be ? ToLength(? Get(O, "length")).
			var len = toInteger(o.length);
			if (len <= 0) {
				len = 0;
			}
			if (len === Infinity) {
				len = Math.pow(2, 53) - 1;
			} else {
				len = Math.min(len, Math.pow(2, 53) - 1);
			}
			len = Math.max(len, 0);

			// 22.1.3.3.3 Let relativeTarget be ? ToInteger(target).
			var relativeTarget = toInteger(target);

			// 22.1.3.3.4 If relativeTarget < 0, let to be max((len + relativeTarget), 0); else let to be min(relativeTarget, len).
			var to;
			if (relativeTarget < 0) {
				to = Math.max(len + relativeTarget, 0);
			} else {
				to = Math.min(relativeTarget, len);
			}

			// 22.1.3.3.5 Let relativeStart be ? ToInteger(start).
			var relativeStart = toInteger(start);

			// 22.1.3.3.6 If relativeStart < 0, let from be max((len + relativeStart), 0); else let from be min(relativeStart, len).
			var from;
			if (relativeStart < 0) {
				from = Math.max(len + relativeStart, 0);
			} else {
				from = Math.min(relativeStart, len);
			}

			// 22.1.3.3.7 If end is undefined, let relativeEnd be len; else let relativeEnd be ? ToInteger(end).
			var relativeEnd;
			if (end === undefined) {
				relativeEnd = len;
			} else {
				relativeEnd = toInteger(end);
			}

			// 22.1.3.3.8 If relativeEnd < 0, let final be max((len + relativeEnd), 0); else let final be min(relativeEnd, len).
			var final;
			if (relativeEnd < 0) {
				final = Math.max(len + relativeEnd, 0);
			} else {
				final = Math.min(relativeEnd, len);
			}

			// 22.1.3.3.9 Let count be min(final-from, len-to).
			var count = Math.min(final - from, len - to);

			// 22.1.3.3.10 If from<to and to<from+count, then
			var direction;
			if (from < to && to < from + count) {
				// 22.1.3.3.10.a Let direction be -1.
				direction = -1;

				// 22.1.3.3.10.b Let from be from + count - 1.
				from = from + count - 1;

				// 22.1.3.3.10.c Let to be to + count - 1.
				to = to + count - 1;
			} else {
				// 22.1.3.3.11 Else,
				// 22.1.3.3.11.a Let direction be 1.
				direction = 1;
			}

			// 22.1.3.3.12 Repeat, while count > 0
			while (count > 0) {
				// 22.1.3.3.12.a Let fromKey be ! ToString(from).
				var fromKey = String(from);
				// 22.1.3.3.12.b Let toKey be ! ToString(to).
				var toKey = String(to);
				// 22.1.3.3.12.c Let fromPresent be ? HasProperty(O, fromKey).
				var fromPresent = hasProperty(o, fromKey);
				// 22.1.3.3.12.d If fromPresent is true, then
				if (fromPresent) {
					// 22.1.3.3.12.d.i Let fromVal be ? Get(O, fromKey).
					var fromVal = o[fromKey];
					// 22.1.3.3.12.d.ii Perform ? Set(O, toKey, fromVal, true).
					o[toKey] = fromVal;
				} else {
					// 22.1.3.3.12.e Else fromPresent is false,
					// 22.1.3.3.12.e.i Perform ? DeletePropertyOrThrow(O, toKey).
					delete o[toKey];
				}
				// 22.1.3.3.12.f Let from be from + direction.
				from = from + direction;
				// 22.1.3.3.12.g Let to be to + direction.
				to = to + direction;
				// 22.1.3.3.12.h Let count be count - 1.
				count = count - 1;
			}
			// 22.1.3.3.13 Return O.
			return o;
		}
	});
}());