text: class Group {
    constructor() {
      this.group = [];
    }
  
    add(value) {
      if (!this.has(value)) {
        this.group.push(value);
      }
    }
  
    delete(value) {
      if (this.has(value)) {
        const removeDelete = this.group.indexOf(value);
        delete this.group[removeDelete];
      }
    }
  
    has(value) {
      for (let member of this.group) {
        if (member === value) {
          return true;
        }
      }
      return false;
    }
  
    static from(iterable) {
      let group = new Group();
      for (let element of iterable) {
        group.add(element);
      }
      return group;
    }
  }
  
  let group = Group.from([10, 20]);
  console.log(group.has(10));
  console.log(group.has(30));
  group.add(10);
  group.delete(10);
  console.log(group.has(10));
  