Hello

About "use strict" inhttps://javascript.info/strict-mode is indicated:

This was the case until 2009 when ECMAScript 5 (ES5) appeared. It added new features to the language and modified some of the existing ones.To keep the old code working, most such modifications are off by default. You need to explicitly enable them with a special directive: "use strict"

The italic part is not very clear (I read the spanish version too), it gives the idea that "use strict" enables the old mode code

Of course inhttps://javascript.info/javascript-specials#strict-mode is more clear with:

To fully enable all features ofmodern JavaScript, we should start scripts with "use strict".

Thank you