JS Set implementation without prototype nonsense

set.js

'use strict';

// A drop-in replacement for Set.
// Why?
//  1) newSet() can be called as a regular function (no need for new)
//  2) None of the functions on it use `this`, which means they can be used as higher-order functions

function newSet(initialValues) {
    const s = new Set();

    const o = {
        // Standard set functions
        add: (value) => { s.add(value); return o; },
        clear: s.clear.bind(s),
        delete: s.delete.bind(s),
        entries: s.entries.bind(s),
        forEach: s.forEach.bind(s),
        has: s.has.bind(s),
        keys: s.keys.bind(s),
        values: s.values.bind(s),
        [Symbol.iterator]: s[Symbol.iterator].bind(s),
        
        // Extra utility methods
        addAll: (values) => { values.forEach(o.add); return o; },
        deleteAll: (values) => values.map(o.delete).some((i) => i),
        hasAll: (values) => values.every(o.has),
        asArray: () => Array.from(o[Symbol.iterator]())
    };

    if (initialValues !== undefined) {
        o.addAll(initialValues);
    }

    return o;
}

// Usage

const s = newSet([1, 2]);
['abc', 'def', 'ghi'].forEach(s.add);
console.log('s has 2: ', s.has(2)); // true
console.log('s has abc: ', s.has('abc')); // true
console.log('s has def: ', s.has('def')); // true
console.log('s has ghi: ', s.has('ghi')); // true
console.log('s has xyz: ', s.has('xyz')); // false

console.log('s has both 1 and 2: ', s.hasAll([1, 2])); // true
console.log('s has both abc and xyz: ', s.hasAll(['abc', 'xyz'])); // false

s.deleteAll([2, 'ghi']);

// Test iteration
for (let x of s) {
    console.log('\t x = ', x);
}

console.log('s = ', s.asArray()); // [ 1, 'abc', 'def' ]

function whyNotRegularSet() {
  const s2 = new Set();
  // The following line will throw.
  // Need to do s2.add.bind(s2) to make this work.
  [1, 2, 3].forEach(s2.add); 
  console.log(s2.has(1));
}