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/* Any copyright is dedicated to the Public Domain.
"use strict";
const x = Object.freeze([1, 2, 3]);
let fakeArray = {
[Symbol.isConcatSpreadable]: true,
length: 2,
0: "hello",
1: "world"
}
assertDeepEq(x.concat(fakeArray), [1, 2, 3, "hello", "world"]);
assertDeepEq(x.concat(fakeArray, fakeArray), [1, 2, 3, "hello", "world", "hello", "world"]);
for (let truthy of [true, 3.41, "abc", Symbol(), {}]) {
let obj = {[Symbol.isConcatSpreadable]: truthy, length: 1, 0: "hey"}
assertDeepEq(x.concat(obj), [1, 2, 3, "hey"]);
}
for (let notTruthy of [null, undefined, false, 0, NaN, ""]) {
let obj = {[Symbol.isConcatSpreadable]: notTruthy, length: 1, 0: "hey"}
assertDeepEq(x.concat(obj), [1, 2, 3, obj]);
}
let array = [5, 4];
assertDeepEq(x.concat(array), [1, 2, 3, 5, 4]);
// Can make arrays non-spreadable
array[Symbol.isConcatSpreadable] = false;
assertDeepEq(x.concat(array), [1, 2, 3, [5, 4]]);
// Explicitly spreadable
array[Symbol.isConcatSpreadable] = true;
assertDeepEq(x.concat(array), [1, 2, 3, 5, 4]);
reportCompare(true, true);