How to implement cheat codes (Javascript)

So I have already looked it up but the simplest one I found was C# and i only know JavaScript. So could someone either convert this into Js for me, or show me different Js code for cheats

 private string[] cheatCode;
 private int index;
  
 void Start() {
     // Code is "idkfa", user needs to input this in the right order
     cheatCode = new string[] { "i", "d", "k", "f", "a" };
     index = 0;  
 }
  
 void Update() {
     // Check if any key is pressed
     if (Input.anyKeyDown) {
         // Check if the next key in the code is pressed
         if (Input.GetKeyDown(cheatCode[index])) {
             // Add 1 to index to check the next key in the code
             index++
         }
         // Wrong key entered, we reset code typing
         else {
             index = 0;  
         }
     }
  
     // If index reaches the length of the cheatCode string, 
     // the entire code was correctly entered
     if (index == cheatCode.Length) {
         // Cheat code successfully inputted!
         // Unlock crazy cheat code stuff
     }
 }