text: 'use strict';
  
  const groups = ['IT-71', 'IT-72', 'IT-73', 'IT-74', 'IP-71', 'IP-72', 'IP-73'];
  
  class SetExample {
    constructor(arr) {
      this.set = arr;
    }
    add(el) {
      this.set.push(el);
    }  
    delete(el) {
      if(this.set.includes(el)) delete this.set[this.set.indexOf(el)];
      else console.log(`Impossible to delete. ${el} does not exsist in this array.`);   
    }
    has(el) {
      if(this.set.includes(el)) console.log(`Array has ${el}.`);
      else console.log(`Array has not ${el}.`);
    }
    replace(el1, el2) {
      if(this.set.includes(el1)) {
        delete this.set[this.set.indexOf(el1)];
        this.set[this.set.indexOf(el1)] = el2;
      } else {
        console.log(`Array has not ${el1}.`);
      }
    }
  }
  
  const FICTgroups = new SetExample(groups);
  FICTgroups.add('IP-74');
  FICTgroups.delete('IP-74');
  FICTgroups.delete('IK-72');
  FICTgroups.has('IP-73');
  FICTgroups.has('IP-74');
  FICTgroups.replace('IT-71', 'IL-71');
  console.log(FICTgroups);
  
  
  