let a = "hello";
  console.log( a );
  let a = "goodbye";

What you're referring to is the fact that when you expand an object or array in the console, then you see the contents of that object or array at the time you expand it, not as it originally existed when console.log() was called.

This is why alessioalex's sibling comment is so useful. By logging the output from JSON.stringify(), you are logging a string whose value will not change.