Yoko Oh Noes confused about hoisting and loops

[lgto4]

See the demo program at https://www.khanacademy.org/computer-programming/confused/5208304615768064 . It attempts to initialize a variable declared inside the body of a loop to undefined causing the complaint "It's not necessary to initialize 't' to 'undefined'." which is certainly not the case.

[pamelafox]

Huh. Thanks for the report, Bob!

[Steffan153]

This is actually one of the really catchy things about JS, it can be pretty confusing. I guess Oh Noes just hasn't learned enough JS to understand 😂

If let/const was supported though, we wouldn't have to worry about this of course.

[1point7point4]

In Ono-chan's defense, it's usually not considered good practice to initialize a variable multiple times in the same scope; I think the more commonplace approach would be something like:

var t;
for (var i = 0; i < 10; i++) {
        t = undefined;
        if (random() < 0.2) {
            t = 1;
        }
        if (t) {
            println(i + ". bingo");
        }
    }

edit: that being said, i still think this should be considered a bug and not a feature

[vijjuu787]

it's usually not considered good practice to initialize a variable multiple times in the same scope.
initialize t=0 ;
`
var t = 0; // Set t to a falsy value initially
var doit = function() {
for (var i = 0; i < 10; i++) {
if (random() < 0.2) {
t = 1;
}
if (t) {
println(i + ". bingo");
}
}
};

doit();
`