Because you can create that array anyway, like so: var arr = []; arr[0] = 1; arr[1] = 2; arr[3] = 3; so there's not really much downside to also allow

Because you can create that array anyway, like so: var arr = []; arr[0] = 1; arr[1] = 2; arr[3] = 3; so there's not really much downside to also allowing a literal syntax for the same thing.