How to use the return output to display it inside an element in the HTML

class Cipher {
    constructor(shift=0, plain_text="", encrypted_string="") {
      this.alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
      this.shift = shift;
      this.plain_text = plain_text;
      this.text_length = 0;
      this.encrypted_string = encrypted_string;
    }
  
    describe() {
      console.log("");
      for (const [attribute, value] of Object.entries(this)) {
        console.log(`${attribute}: ${value}`);
      }
      console.log("");
    }
  
    setShift(shiftValue) {
      this.shift = shiftValue;
    }
  
    setPlainText(plainText) {
      this.plain_text = plainText;
    }
  
    setTextLength() {
      this.text_length = this.plain_text.length;
    }
  
    encrypt() {
      for (let i = 0; i < this.text_length; i++) {
        let char = this.plain_text[i].toUpperCase();
        if (char === " ") {
          this.encrypted_string += char;
        } else {
          let location = this.alphabet.indexOf(char);
          let new_location = (location + this.shift) % 26;
          this.encrypted_string += this.alphabet[new_location];
        }
      }
      return this.encrypted_string;
    }
}

const shift = document.getElementById("shiftInput")
const plaintext = document.getElementById("plainTextArea")
const encryptBtn = document.getElementById("encryptBtn")
const encryptedString = document.getElementById("encryptedArea")

const cipherObj01 = new Cipher();

function displayOutput() {
    cipherObj01.setShift(shift.value);
    cipherObj01.setPlainText(plaintext.value);
    cipherObj01.setTextLength();
    
    const encryption = cipherObj01.encrypt()
    
    encryptedString.value = encryption;
}

encryptBtn.addEventListener('click', displayOutput());

class Cipher {
    constructor(shift=0, plain_text="", encrypted_string="") {
      this.alphabet = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
      this.shift = shift;
      this.plain_text = plain_text;
      this.text_length = 0;
      this.encrypted_string = encrypted_string;
    }
  
    describe() {
      console.log("");
      for (const [attribute, value] of Object.entries(this)) {
        console.log(`${attribute}: ${value}`);
      }
      console.log("");
    }
  
    setShift(shiftValue) {
      this.shift = shiftValue;
    }
  
    setPlainText(plainText) {
      this.plain_text = plainText;
    }
  
    setTextLength() {
      this.text_length = this.plain_text.length;
    }
  
    encrypt() {
      for (let i = 0; i < this.text_length; i++) {
        let char = this.plain_text[i].toUpperCase();
        if (char === " ") {
          this.encrypted_string += char;
        } else {
          let location = this.alphabet.indexOf(char);
          let new_location = (location + this.shift) % 26;
          this.encrypted_string += this.alphabet[new_location];
        }
      }
      return this.encrypted_string;
    }
}

const shift = document.getElementById("shiftInput")
const plaintext = document.getElementById("plainTextArea")
const encryptBtn = document.getElementById("encryptBtn")
const encryptedString = document.getElementById("encryptedArea")

const cipherObj01 = new Cipher();

function displayOutput() {
    cipherObj01.setShift(shift.value);
    cipherObj01.setPlainText(plaintext.value);
    cipherObj01.setTextLength();
    
    const encryption = cipherObj01.encrypt()
    
    encryptedString.value = encryption;
}

encryptBtn.addEventListener('click', displayOutput());