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