You shouldn't be allowed near computers.

// Wrap an array of 5 elements.  
var array = wrapArray([0, 1, 2, 3, 4])
...

// Outputs: 3  
console.log(array[-1]);

Nope: it would return 4. :)
Speaking of which, it also seems that "-0" would be parsed to array.length - 0 == array.length, giving us undefined... So I guess the lack of forEach etc is not even the main problem of this naive implementation. :)
Other than that, a very interesting article!

Hmm, the first example is wrong as [0,1,2,3,4][-1] will output 4 in Python (-1 = get the last thing).

This is a nice write up. I had the same idea a while back and wrote this function:

function sliceArray(array=[]) {
  return new Proxy(array, {
    get(target, key) {
      const sliceMatch = key.match(/^(-?\d+)?:(-?\d+)?$/);
      if(sliceMatch) {
        const [/* match */, startIndex=0, endIndex=target.length ] = sliceMatch;
        return sliceArray(target.slice(+startIndex, +endIndex));
      }
      return target[key];
    }
  });
}

const a = sliceArray([1,2,3,4,5,6,7,8,9,10]);

console.log(a['3:-2']['1:']); // outputs: [5, 6, 7, 8]

I opted to use the native Array.prototype.slice since it handles negative indexes (I didn't think to add a step input, but it's not supported by slice anyway).

I’m not exactly sure how good it would be, but there are likely things you could exchange with PyBee’s Batavia project, which implements Python on top of JavaScript. They already have Python lists and slices sort out. They would love any help to correct the implementation if you find any problems as well!

• list: https://github.com/pybee/batavia/blob/master/batavia/types/List.js
• slice: https://github.com/pybee/batavia/blob/master/batavia/types/Slice.js