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function main(x) { // x identifies from which button call is being made: Encrypt or Decrypt

var entry_text = document.getElementById('entry').value

var key_val = parseInt(document.getElementById('key').value) // Reading and storing both the inputs

// if (key_val < 0) {

// alert("Key value cannot be negative")

// }

key_val = key_val % 26

if (x === 2) {

key_val = (-1) * key_val // If call is for Decrypt then key value entered becomes negative

}

var final_string = ""

for (var i = 0; i < entry_text.length; i++) {

final_string = final_string + change(entry_text.charAt(i), key_val)

}

out_ele = document.getElementById('output')

out_ele.style.display = final_string === "" ? "none" : "flex"

out_ele.innerHTML = final_string

}

function isUpperCase(str) { // function to check if letter/word is uppercase or not

return str === str.toUpperCase()

}

function change(ch, key) { // function to shift alphabets according to the key value

if (!(/[a-zA-Z]/).test(ch)) { // checks for symbol and returns without any change if found

return ch

}

if (isUpperCase(ch)) {

let no = (ch.charCodeAt(0) + key - 65) % 26 + 65

if (no < 65) {

return (String.fromCharCode(no + 26))

}

else {

return (String.fromCharCode(no))

}

}

else {

let no = (ch.charCodeAt(0) + key - 97) % 26 + 97

if (no < 97) {

return (String.fromCharCode(no + 26))

}

else {

return (String.fromCharCode(no))

}

}

}