How do I convert textarea to display something else(for example base64 decryption) with javascript?

Issue

I’m trying to create a decrypt page in HTML. I can get the input, and show it as output, but I am confused on how to change the text in the middle. Here is my code so far:
http://jsfiddle.net/RZwmX/1.

HTML:

<textarea name="CipherText" id="CipherText" placeholder="Enter ciphertext here:"></textarea>
<div id="prevCom"></div>

Javascript:

wpcomment.onkeyup = wpcomment.onkeypress = function(){
        wpcomment=btoa(wpcomment);
    document.getElementById('prevCom').innerHTML = this.value;
}

//////////////////////////////////////
//from: https://scotch.io/tutorials/how-to-encode-and-decode-strings-with-base64-in-javascript
// Define the string
var string = 'Hello World!';

// Encode the String
var encodedString = btoa(string);
console.log(encodedString); // Outputs: "SGVsbG8gV29ybGQh"

// Decode the String
var decodedString = atob(encodedString);
console.log(decodedString); // Outputs: "Hello World!"

I am getting the code from https://scotch.io/tutorials/how-to-encode-and-decode-strings-with-base64-in-javascript. Base64 is just one example. What I want to know is how do I do the transition. In my JSFiddle on line 3 of the javascript is how I thought of implementing the conversion, but that doesn’t work.

Solution

I would do something like this:

const input = document.querySelector('#encoded-input')
const output = document.querySelector('#decoded-output')

input.oninput = e => {
  try {
    output.innerText = atob(e.target.value)
  } catch (error) {
    output.innerText = e.target.value
      ? 'Please enter a valid Base64 encoded value.'
      : ''
  }
}

<textarea id="encoded-input"></textarea>
<div id="decoded-output"></div>

Answered By – Eyal C

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