solution.js

/**
 * Initialize your data structure here.
 */
var MyHashSet = function() {
    this.buckets = new Array(1000000)
    this.buckets.fill(0)
};

/** 
 * @param {number} key
 * @return {void}
 */
MyHashSet.prototype.add = function(key) {
    this.buckets[key] = 1
};

/** 
 * @param {number} key
 * @return {void}
 */
MyHashSet.prototype.remove = function(key) {
    this.buckets[key] = 0
};

/**
 * Returns true if this set did not already contain the specified element 
 * @param {number} key
 * @return {boolean}
 */
MyHashSet.prototype.contains = function(key) {
    return this.buckets[key] === 1
};

/** 
 * Your MyHashSet object will be instantiated and called as such:
 * var obj = Object.create(MyHashSet).createNew()
 * obj.add(key)
 * obj.remove(key)
 * var param_3 = obj.contains(key)
 */