They do, but strings that are numbers will be reinterpreted as numbers.

[edit]

  let testArray = [];
  testArray[0] = "foo";
  testArray["0"] = "bar";
  testArray["00"] = "baz";
  console.log(testArray[0]);
  console.log(testArray["0"]);
  console.log(testArray["00"]);

That example only shows the opposite of what it sounds like you’re saying, although you could be getting at a few different true things. Anyway:

- Every property access in JavaScript is semantically coerced to a string (or a symbol, as of ES6). All property keys are semantically either strings or symbols.

- Property names that are the ToString() of a 31-bit unsigned integer are considered indexes for the purposes of the following two behaviours:

- For arrays, indexes are the elements of the array. They’re the properties that can affect its `length` and are acted on by array methods.

- Indexes are ordered in numeric order before other properties. Other properties are in creation order. (In some even nicher cases, property order is implementation-defined.)

  { let a = {}; a['1'] = 5; a['0'] = 6; Object.keys(a) }
  // ['0', '1']

  { let a = {}; a['1'] = 5; a['00'] = 6; Object.keys(a) }
  // ['1', '00']