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'use strict'; var $ = require('../internals/export'); var toObject = require('../internals/to-object'); var lengthOfArrayLike = require('../internals/length-of-array-like'); var setArrayLength = require('../internals/array-set-length'); var deletePropertyOrThrow = require('../internals/delete-property-or-throw'); var doesNotExceedSafeInteger = require('../internals/does-not-exceed-safe-integer');
// IE8-
var INCORRECT_RESULT = [].unshift(0) !== 1;
// V8 ~ Chrome < 71 and Safari <= 15.4, FF < 23 throws InternalError
var properErrorOnNonWritableLength = function () { try { // eslint-disable-next-line es/no-object-defineproperty -- safe
Object.defineProperty([], 'length', { writable: false }).unshift(); } catch (error) { return error instanceof TypeError; } };
var FORCED = INCORRECT_RESULT || !properErrorOnNonWritableLength();
// `Array.prototype.unshift` method
// https://tc39.es/ecma262/#sec-array.prototype.unshift
$({ target: 'Array', proto: true, arity: 1, forced: FORCED }, { // eslint-disable-next-line no-unused-vars -- required for `.length`
unshift: function unshift(item) { var O = toObject(this); var len = lengthOfArrayLike(O); var argCount = arguments.length; if (argCount) { doesNotExceedSafeInteger(len + argCount); var k = len; while (k--) { var to = k + argCount; if (k in O) O[to] = O[k]; else deletePropertyOrThrow(O, to); } for (var j = 0; j < argCount; j++) { O[j] = arguments[j]; } } return setArrayLength(O, len + argCount); } });
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