4 ms·

Wow, this truly is an "array with a hash/dict at the end" arr = [] arr[-1] = 'neg-one-key' arr[0] = 'zero-pos' arr[1] = 'one-pos' arr[2] = 'two-pos'

Wow, this truly is an "array with a hash/dict at the end" arr = [] arr[-1] = 'neg-one-key' arr[0] = 'zero-pos' arr[1] = 'one-pos' arr[2] = 'two-pos' arr[-2] = 'neg-two-key' arr[3] = 'three-pos' arr // => ["zero-pos", "one-pos", "two-pos", "three-pos", -1: "neg-one-key", -2: "neg-two-key"] arr.splice(2, 1) arr // => ["zero-pos", "one-pos", "three-pos", -1: "neg-one-key", -2: "neg-two-key"] arr[3] // => undefined Incredibly weird for me.

goatlover 6y ago
That’s because arrays are also objects in JS, and objects can have new properties added, which are implemented as hash strings. Everything in JS is a kind of object, including functions.
- Jack_Hacker 6y ago
  Not quite everything. JavaScript does have some primitives, though it also provides object wrappers for those primitives via the new operator. > let numberPrimitive = 0; undefined > let numberObject = new Number(0); undefined > typeof(numberPrimitive); 'number' > typeof(numberObject); 'object' > typeof(numberObject + numberObject); 'number' > numberPrimitive; 0 > numberObject; [Number: 0] > numberPrimitive.one = 1; 1 > numberObject.one = 1; 1 > numberPrimitive.one; undefined > numberObject.one; 1 > numberPrimitive; 0 > numberObject; [Number: 0] { one: 1 }
  - ulucs 6y ago
    Just using parenthesis is enough for wrapping: > 0.toString() Thrown: 0.toString() ^^ SyntaxError: Invalid or unexpected token > (0).toString() '0'
    - Jack_Hacker 6y ago
      Parens aren't doing the same thing. Primitives are implicitly being wrapped in objects when you use methods, but they come out on the other end as primitives again. The new operator gives you an object wrapper that you can keep working with and modifying the values of, whereas the parens you're using just let the interpreter know that your period isn't a decimal point. You can also use a space for this. > typeof(new Number(0)); 'object' > typeof((0)); 'number' > 0 .toString(); '0'

goatlover 6y ago

That’s because arrays are also objects in JS, and objects can have new properties added, which are implemented as hash strings. Everything in JS is a kind of object, including functions.

Jack_Hacker 6y ago
Not quite everything. JavaScript does have some primitives, though it also provides object wrappers for those primitives via the new operator. > let numberPrimitive = 0; undefined > let numberObject = new Number(0); undefined > typeof(numberPrimitive); 'number' > typeof(numberObject); 'object' > typeof(numberObject + numberObject); 'number' > numberPrimitive; 0 > numberObject; [Number: 0] > numberPrimitive.one = 1; 1 > numberObject.one = 1; 1 > numberPrimitive.one; undefined > numberObject.one; 1 > numberPrimitive; 0 > numberObject; [Number: 0] { one: 1 }
- ulucs 6y ago
  Just using parenthesis is enough for wrapping: > 0.toString() Thrown: 0.toString() ^^ SyntaxError: Invalid or unexpected token > (0).toString() '0'
  - Jack_Hacker 6y ago
    Parens aren't doing the same thing. Primitives are implicitly being wrapped in objects when you use methods, but they come out on the other end as primitives again. The new operator gives you an object wrapper that you can keep working with and modifying the values of, whereas the parens you're using just let the interpreter know that your period isn't a decimal point. You can also use a space for this. > typeof(new Number(0)); 'object' > typeof((0)); 'number' > 0 .toString(); '0'