Initilization of a var to 'undefined' in a loop gives wrong error

[jontra]

for (var i=0; i<10; i++)
{
    var a = undefined;
    if (i%2)
        a = 1;
    if (a===undefined)
        console.log("error");
}

test.js: line 3, col 9, It's not necessary to initialize 'a' to 'undefined'.

It is necessary, since 'a' is not in the 'for' block scope.

[WolfgangKluge]

hmm, there's nothing like a for-block scope in javascript.
To fix this issue, we have to prevent the error message if undefined is assigned to a new variable inside a loop statement. I'd like to have more discussion on that ;)

However, I think you're right - personally, I try to avoid undefined in any script. It's not a keyword and could be overwritten with any other value in non-strict code (var undefined = 1;).
So it might be a better idea to set the value to null.

As a workaround, you can use

var a;
for (var i=0; i<10; i++)
{
    a = undefined;
    if (i%2)
        a = 1;
    if (a===undefined)
        console.log("error");
}

Greetings, Wolfgang

[pvdz]

(Interesting choice to close #1142 for this issue, but whatever :) I think my main beef was that the error was non-ignorable, but I'm not sure about that at this point. )

[stevage]

Whee, this is an old issue. Just came here to chime in about #1142. I ran into a bug in my code where the right answer was to change var foo; to var foo=undefined;, so it's pretty irritating to then have JSHint tell me that it's "not necessary".

[lukeapage]

@stevage there you go, I made a PR to fix it.

I can also confirm that disabling W080 e.g. // jshint -W080 does work on master

[stevage]

Whoa, thank you! :)

[pvdz]

👍