typescript shuffling an array using new constructor classes

shuffle.ts

interface ContactInf {
  name: string;
  numbers: (number|string)[];
}

class Contact implements ContactInf {
  constructor (public name: string, public numbers: (number|string)[]) {
    console.info('creating');
  };
  // new es6 style 
  
  getName() {
    this.name;
  }

  getNum() {
    this.numbers;
  }

};

// old style es5 way
// Contact.prototype.getName = ():string => this.name;

// Contact.prototype.getNum = ():string =>  this.numbers;

const
  ar = ['a', 'b', 'c'],
  d = [0, 1, 2, ...ar, 3, 4],
  contact = new Contact('mat', d),
  {name: matName, numbers: matNumbers} = contact,
  ceilRandom = (ln: number, idx: number):number => {
    return Math.floor((Math.random() * idx * 10)%ln);
    },
  shuffle = (arr: (number|string)[]) => {
    let 
      ln:number = arr.length,
      upper:number = 0; 

    for (let idx:number=0; idx < ln; idx++) {
      upper = ceilRandom(ln, idx);
      // console.info(`idx: ${idx}; upper: ${upper}; ln: ${ln}`);
      let tmp = arr[upper];
      arr[upper] = arr[idx];
      arr[idx] = tmp;
      // console.info(arr);
    }
    return arr;
  };

console.info(shuffle(matNumbers));