main.js

// URL: https://leetcode.com/problems/design-hashset/

var MyHashSet = function () {
    this.set = {};
};

/** 
 * @param {number} key
 * @return {void}
 */
MyHashSet.prototype.add = function (key) {
    if (!this.contains(key))
        this.set.push(key)
};

/** 
 * @param {number} key
 * @return {void}
 */
MyHashSet.prototype.remove = function (key) {
    if (this.contains(key))
        this.set = this.set.filter(item => item !== key);
};

/** 
 * @param {number} key
 * @return {boolean}
 */
MyHashSet.prototype.contains = function (key) {
    return this.set.find(item => item === key) !== undefined;
};

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