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10.4.2 Array Exotic Objects
https://tc39.es/ecma262/#sec-array-exotic-objects
A String property name P is an array index if and only if
ToString(ToUint32(P)) equals P and ToUint32(P) is not the same value
as 𝔽(2^32 - 1).
30 lines
821 B
JavaScript
30 lines
821 B
JavaScript
test("numeric properties", () => {
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const i32Max = 2 ** 31 - 1;
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const u32Max = 2 ** 32 - 1;
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const o = {
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[-1]: "foo",
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0: "foo",
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1: "foo",
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[i32Max - 1]: "foo",
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[i32Max]: "foo",
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[i32Max + 1]: "foo",
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[u32Max - 1]: "foo",
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[u32Max]: "foo",
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[u32Max + 1]: "foo",
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};
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// Numeric properties come first in Object.getOwnPropertyNames()'s output,
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// which means we can test what each is treated as internally.
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expect(Object.getOwnPropertyNames(o)).toEqual([
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// Numeric properties
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"0",
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"1",
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"2147483646",
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"2147483647",
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"2147483648",
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"4294967294",
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// Non-numeric properties
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"-1",
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"4294967295", // >= 2^32 - 1
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"4294967296", // >= 2^32 - 1
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]);
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});
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