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AI solution for JavaScript Quiz on BFE.dev
90. array keys
The code outputs the following:
["length"]
["0", "length"]
["0", "2", "length"]
["0", "2", "length"]
Explanation:
Reflect.ownKeys([])
returns an array containing only the "length" property, because the array is empty.Reflect.ownKeys([,])
returns an array containing "0" and "length", because the array has one element but with an empty slot (trailing comma notation).Reflect.ownKeys([1,,2])
returns an array containing "0", "2", and "length", because the array has 3 elements, but the middle one is empty (comma notation).Reflect.ownKeys([...[1,,2]])
first creates a new array[1,,2]
with an empty slot, then uses the spread operator to create a new array with the same elements. The resulting array has the same keys as the previous case.