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Comment by erkl | Hacker News Reader

This throws an error:

    typeof x; // throws an error
    let x = 1;

This doesn't:

    typeof x; // returns "undefined"
    var x = 1;

While using variables before declaring them is bad practice, I think it's fair to argue that this behaviour is inconsistent.

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    let x = 0;
    function typeof_wrapper(y) { return typeof y; }

    (function() {
        typeof_wrapper(x); // throws an error
        let x = 1;
    })();

    (function() {
        typeof_wrapper(x); // returns "undefined"
        var x = 1;
    })();

Again, typeof isn't throwing the error, the runtime is, because a variable declared with "let" is being referenced before the declaration. It's not inconsistent, it's one of the main points of "let".

You're essentially arguing that a feature added because the old behaviour was undesirable is inconsistent because it's not exhibiting the old undesirable behaviour.

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