--- /dev/null
+'use strict';
+var toObject = require('../internals/to-object');
+var toAbsoluteIndex = require('../internals/to-absolute-index');
+var toLength = require('../internals/to-length');
+
+var min = Math.min;
+
+// `Array.prototype.copyWithin` method implementation
+// https://tc39.es/ecma262/#sec-array.prototype.copywithin
+module.exports = [].copyWithin || function copyWithin(target /* = 0 */, start /* = 0, end = @length */) {
+ var O = toObject(this);
+ var len = toLength(O.length);
+ var to = toAbsoluteIndex(target, len);
+ var from = toAbsoluteIndex(start, len);
+ var end = arguments.length > 2 ? arguments[2] : undefined;
+ var count = min((end === undefined ? len : toAbsoluteIndex(end, len)) - from, len - to);
+ var inc = 1;
+ if (from < to && to < from + count) {
+ inc = -1;
+ from += count - 1;
+ to += count - 1;
+ }
+ while (count-- > 0) {
+ if (from in O) O[to] = O[from];
+ else delete O[to];
+ to += inc;
+ from += inc;
+ } return O;
+};