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- 'use strict';
- var $ = require('../internals/export');
- var global = require('../internals/global');
- var fails = require('../internals/fails');
- var isArray = require('../internals/is-array');
- var isObject = require('../internals/is-object');
- var toObject = require('../internals/to-object');
- var lengthOfArrayLike = require('../internals/length-of-array-like');
- var createProperty = require('../internals/create-property');
- var arraySpeciesCreate = require('../internals/array-species-create');
- var arrayMethodHasSpeciesSupport = require('../internals/array-method-has-species-support');
- var wellKnownSymbol = require('../internals/well-known-symbol');
- var V8_VERSION = require('../internals/engine-v8-version');
- var IS_CONCAT_SPREADABLE = wellKnownSymbol('isConcatSpreadable');
- var MAX_SAFE_INTEGER = 0x1FFFFFFFFFFFFF;
- var MAXIMUM_ALLOWED_INDEX_EXCEEDED = 'Maximum allowed index exceeded';
- var TypeError = global.TypeError;
- // We can't use this feature detection in V8 since it causes
- // deoptimization and serious performance degradation
- // https://github.com/zloirock/core-js/issues/679
- var IS_CONCAT_SPREADABLE_SUPPORT = V8_VERSION >= 51 || !fails(function () {
- var array = [];
- array[IS_CONCAT_SPREADABLE] = false;
- return array.concat()[0] !== array;
- });
- var SPECIES_SUPPORT = arrayMethodHasSpeciesSupport('concat');
- var isConcatSpreadable = function (O) {
- if (!isObject(O)) return false;
- var spreadable = O[IS_CONCAT_SPREADABLE];
- return spreadable !== undefined ? !!spreadable : isArray(O);
- };
- var FORCED = !IS_CONCAT_SPREADABLE_SUPPORT || !SPECIES_SUPPORT;
- // `Array.prototype.concat` method
- // https://tc39.es/ecma262/#sec-array.prototype.concat
- // with adding support of @@isConcatSpreadable and @@species
- $({ target: 'Array', proto: true, forced: FORCED }, {
- // eslint-disable-next-line no-unused-vars -- required for `.length`
- concat: function concat(arg) {
- var O = toObject(this);
- var A = arraySpeciesCreate(O, 0);
- var n = 0;
- var i, k, length, len, E;
- for (i = -1, length = arguments.length; i < length; i++) {
- E = i === -1 ? O : arguments[i];
- if (isConcatSpreadable(E)) {
- len = lengthOfArrayLike(E);
- if (n + len > MAX_SAFE_INTEGER) throw TypeError(MAXIMUM_ALLOWED_INDEX_EXCEEDED);
- for (k = 0; k < len; k++, n++) if (k in E) createProperty(A, n, E[k]);
- } else {
- if (n >= MAX_SAFE_INTEGER) throw TypeError(MAXIMUM_ALLOWED_INDEX_EXCEEDED);
- createProperty(A, n++, E);
- }
- }
- A.length = n;
- return A;
- }
- });
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