ArrayMemberAccessFilter.js

/**
 * I reckon computed member access in JS, i.e. ...[...],
 * could be a tonne more powerful. This is an example of that.
 * ===========================================================
 * This is a filthy hack. Probably don't use it...
 * ===========================================================
 * It sets up a proxy that'll catch member access to arrays.
 * Upon member-access, toString will be natively called and
 * intercepted; the intercepted value will be used within our
 * proxy to return a filtered version of the array.
 */
((filterFn, filterArr) => {
  const aps = Array.prototype.toString,
        fps = Function.prototype.toString;
  
  Function.prototype.toString = function() {
    return fps.apply(filterFn = this, arguments) };
  Array.prototype.toString = function() {
    return aps.apply(filterArr = this, arguments) };

  Object.setPrototypeOf(Array.prototype, new Proxy(
    {}, {
      get: function(target, prop, receiver) { 
        return Reflect.get(...arguments) || (
          filterFn && prop === fps.call(filterFn) ?
            receiver.filter(filterFn) :
          filterArr && prop === aps.call(filterArr) ?
            filterArr.map(fn => receiver.filter(fn))
          : undefined );
      }
    }
  ));
})();

// Filter just those numbers less than 4
[1, 2, 3, 4, 5][ n => n < 4 ]; // => [1, 2, 3]

// Filter numbers larger than and less than five into two arrays:
[1, 2, 3, 4, 5, 6, 7, 8, 9][[
  n => n < 5,
  n => n > 5
]]; // => [[1, 2, 3, 4], [6, 7, 8, 9]]

// More examples.....

const [odd, even] = [0, 1, 2, 3, 3, 4, 5, 6][[
  n => n % 2,
  n => !(n % 2)
]]; // => [[1, 3, 5], [0, 2, 6]]

const [
  empty,
  local, 
  remote
] = [...document.querySelectorAll('a')][[
  a => !a.href,
  a => a.hostname === location.hostname,
  a => a.hostname !== location.hostname 
]];