array-copy-within.js
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array-copy-within.js
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	'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
	// eslint-disable-next-line es/no-array-prototype-copywithin -- safe
	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;
	};