technical review - [email protected] about you-dont-know-js HOT 8 CLOSED

https://github.com/getify/You-Dont-Know-JS/blob/master/scope%20&%20closures/ch2.md
Line 23

This example introduces an unnecessary level of indirection with declarations ordered as a, c, b.

function foo(a) {

    function bar(c) {
        console.log(a, b, c);
    }

    var b = a * 2;

    bar(b * 3);
}

foo(2); // 2, 4, 12

It could be more simply written like so:

function foo(a) {
    var b = a * 2;

    function bar(c) {
        console.log(a, b, c);
    }

    bar(b * 3);
}

foo(2); // 2, 4, 12

Yes hoisting could be considered an issue, but there is no need to worry about it here since it has yet to be introduced. This order allows the reader to follow the a, b, c declarations instead of a, c, b.

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https://github.com/getify/You-Dont-Know-JS/blob/master/scope%20&%20closures/ch2.md

Cheating with eval:
Is it worth mentioning Function constructor declarations here? They perform a flavor of eval and can produce global variables.

new Function('x = "global carnage!";');

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https://github.com/getify/You-Dont-Know-JS/blob/master/scope%20&%20closures/ch3.md

While discussing passing vars to IIFE's it might be nice to mention the undefined pattern since it is quite prevalent and likely to be encountered in the wild.

(function (global, undefined) {
    var a;
    if (a === undefined) {
        console.log('nothing here!');
    }
})(window);

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https://github.com/getify/You-Dont-Know-JS/blob/master/scope%20&%20closures/ch4.md
Line 92

I believe you intended this:

function foo() {
    var a;

    console.log(a); // undefined

    a = 2;
}

foo();

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https://github.com/eborden/You-Dont-Know-JS/blob/master/scope%20&%20closures/ch5.md

I'm not seeing the let/loop behavior that you are prescribing in the latest IE. This could be an implementation detail.

for(let i = 0; i < 4; i++){
    let j = i;
    setTimeout(function () {
        alert(i); // 4 4 4 4
        alert(j); // 0 1 2 3
    }, 10);
}

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Note, tested the previous example in the latest FF and had the same results.

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None of the browsers are conforming (yet) on the for (let x = ... behavior of binding per iteration. Here's a mozilla bug tracking their (dormant) attempt to come into alignment with the spec on this topic.

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Thanks for all the great feedback. I've finished posting revisions that take your comments into account.

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