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// Copyright (C) 2020 Alexey Shvayka. All rights reserved.
// This code is governed by the BSD license found in the LICENSE file.
/*---
esid: sec-array.prototype.concat
description: >
Symbol.isConcatSpreadable should be looked up once for `this value` and
once for each argument, after ArraySpeciesCreate routine.
info: |
Array.prototype.concat ( ...arguments )
1. Let O be ? ToObject(this value).
2. Let A be ? ArraySpeciesCreate(O, 0).
[...]
5. Repeat, while items is not empty
a. Remove the first element from items and let E be the value of the element.
b. Let spreadable be ? IsConcatSpreadable(E).
[...]
ArraySpeciesCreate ( originalArray, length )
[...]
5. Let C be ? Get(originalArray, "constructor").
[...]
Runtime Semantics: IsConcatSpreadable ( O )
1. If Type(O) is not Object, return false.
2. Let spreadable be ? Get(O, @@isConcatSpreadable).
[...]
includes: [compareArray.js]
features: [Symbol.isConcatSpreadable]
---*/
var calls = [];
var descConstructor = {
get: function() {
calls.push("constructor");
return Array;
},
configurable: true,
};
var descSpreadable = {
get: function() {
calls.push("isConcatSpreadable");
},
configurable: true,
};
var arr1 = [];
Object.defineProperty(arr1, "constructor", descConstructor);
Object.defineProperty(arr1, Symbol.isConcatSpreadable, descSpreadable);
assert.compareArray(arr1.concat(1), [1], 'arr1.concat(1) must return [1]');
assert.compareArray(
calls,
["constructor", "isConcatSpreadable"],
'The value of calls is expected to be ["constructor", "isConcatSpreadable"]'
);
calls = [];
var arr2 = [];
var arg = {};
Object.defineProperty(arr2, "constructor", descConstructor);
Object.defineProperty(arg, Symbol.isConcatSpreadable, descSpreadable);
assert.compareArray(arr2.concat(arg), [arg], 'arr2.concat({}) must return [arg]');
assert.compareArray(
calls,
["constructor", "isConcatSpreadable"],
'The value of calls is expected to be ["constructor", "isConcatSpreadable"]'
);
reportCompare(0, 0);
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