[1, 2, 3].fill(4) // [4, 4, 4]
[1, 2, 3].fill(4, 1) // [1, 4, 4]
[1, 2, 3].fill(4, 1, 2) // [1, 4, 3]
[1, 2, 3].fill(4, 1, 1) // [1, 2, 3]
[1, 2, 3].fill(4, 3, 3) // [1, 2, 3]
[1, 2, 3].fill(4, -3, -2) // [4, 2, 3]
[1, 2, 3].fill(4, NaN, NaN) // [1, 2, 3]
[1, 2, 3].fill(4, 3, 5) // [1, 2, 3]
Array(3).fill(4) // [4, 4, 4]
[].fill.call({ length: 3 }, 4) // {0: 4, 1: 4, 2: 4, length: 3}
// A single object, referenced by each slot of the array:
let arr = Array(3).fill({}) // [{}, {}, {}]
arr[0].hi = "hi" // [{ hi: "hi" }, { hi: "hi" }, { hi: "hi" }]