| '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.github.io/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; |
| }; |