Object.prototype.__proto__ polyfill for ES6 (if the runtime *doesn't* implement it -- it's technically optional for non-web browsers)

proto.js

/**
 * By Isiah Meadows.
 * This code is licensed under CC0 1.0 Universal. You can get a copy of the license at https://creativecommons.org/publicdomain/zero/1.0/legalcode.txt
 */

if (!function (F) {
    return {}.__proto__ === Object.prototype; // Also if it's broken
}(function () {}) && Object.getPrototypeOf && Object.setPrototypeOf) {
    Object.defineProperty(Object.prototype, '__proto__', {
        'get': function () {
            return Object.getPrototypeOf(this);
        },
        'set': function (proto) {
            return Object.setPrototypeOf(this, proto);
        }
    });
}

proto.min.js

/*By Isiah Meadows. This code is licensed under CC0 1.0 Universal. You can get a copy of the license at https://creativecommons.org/publicdomain/zero/1.0/legalcode.txt*/Object.prototype!=={}.__proto__&&Object.getPrototypeOf&&Object.setPrototypeOf&&Object.defineProperty(Object.prototype,'__proto__',{'set':function(p){return Object.setPrototypeOf(this,p)},'get':function(){return Object.getPrototypeOf(this)}});

More performant version:

/**
 * By Isiah Meadows, then edited by Jack and 
 * This code is licensed under CC0 1.0 Universal. You can get a copy of the license at https://creativecommons.org/publicdomain/zero/1.0/legalcode.txt
 */

if (({}).__proto__ !== Object.prototype) (function(getPrototypeOf, setPrototypeOf){
    Object.defineProperty(Object.prototype, '__proto__', {
        'get': function () {
            return getPrototypeOf(this);
        },
        'set': function (proto) {
            return setPrototypeOf(this, proto);
        }
    });
})(Object.getPrototypeOf, Object.setPrototypeOf);