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Issue with IE11 and missing Symbol.iterator #1850

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Merged
merged 1 commit into from
Jul 15, 2021
Merged

Issue with IE11 and missing Symbol.iterator #1850

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14 changes: 14 additions & 0 deletions __tests__/List.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -724,6 +724,20 @@ describe('List', () => {
expect(v2.toArray()).toEqual([1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, null]);
});

it('concat works like Array.prototype.concat even for IE11', () => {
const v1 = List([1, 2, 3]);
const a = [4];

// remove Symbol.iterator as IE11 does not handle it.
// See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/@@iterator#browser_compatibility
// @ts-expect-error -- simulate IE11
a[Symbol.iterator] = undefined;

const v2 = v1.concat(a);
expect(v1.toArray()).toEqual([1, 2, 3]);
expect(v2.toArray()).toEqual([1, 2, 3, 4]);
});

it('concat returns self when no changes', () => {
const v1 = List([1, 2, 3]);
expect(v1.concat([])).toBe(v1);
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5 changes: 5 additions & 0 deletions src/Iterator.js
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Expand Up @@ -44,6 +44,11 @@ export function iteratorDone() {
}

export function hasIterator(maybeIterable) {
if (Array.isArray(maybeIterable)) {
// IE11 trick as it does not support `Symbol.iterator`
return true;
}

return !!getIteratorFn(maybeIterable);
}

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