Error running console command in Firefox?

Question

JavaScript

I noticed a strange thing in the Firefox console - the first time it executes the command, and all subsequent times it gives an error. I'll give an example:

let age = prompt('Сколько тебе лет?');
alert(`Тебе ${age} лет!`);

The first time it runs without any complaints, and the next time it gives out: And this is exactly in the desktop Firefox (version 84.0.2), in the Chrome console there are no problems with this. Why is that?

Uncaught SyntaxError: redeclaration of let age

Answer 1

Because formally you call something like this

let age = prompt('Сколько тебе лет?');
alert(`Тебе ${age} лет!`);

let age = prompt('Сколько тебе лет?');
alert(`Тебе ${age} лет!`);

The variable age is declared twice within the same context. Which is a mistake. Chromium behaved the same way until recently. Then, he allowed to re-declare variables directly in the console using let / const

Answer 2

Use Console Features varinstead andletlet

let x;
let x; // ошибка: переменная x уже объявлена