Array with a negative length!

gistfile1.txt

'use strict';

const OriginalArray = global.Array;

global.Array = function Array(...args) {
  const arr = new OriginalArray(...args);
  let length = arr.length;
  return new Proxy(arr, {
    set(target, propKey, value, Receiver) {
      if (propKey === 'length') {
        const cast1 = +value;
        const cast2 = value >>> 0;
        if (cast1 !== cast2) {
          length = cast1;
          return true;
        }
      }
      const res = Reflect.set(target, propKey, value, Receiver);
      length = target.length;
      return res;
    },
    get(target, propKey, Receiver) {
      if (propKey === 'length') {
        return length;
      }
      return Reflect.get(target, propKey, Receiver);
    }
  });
};
global.Array.isArray = OriginalArray.isArray;
global.Array.prototype = OriginalArray.prototype;

const newArray = new Array();
console.log(Array.isArray(newArray));
// Prints true!

newArray.length = -1;
console.log(newArray.length);
// Prints -1!