adding eval inside a function puts all variables into global through

[ilyavolodin]

The following code:

function evilEval(stuffToEval)
{
    var ultimateAnswer;

    ultimateAnswer = 42;

    alert(stuffToEval);
}

Will put one variable into through array - alert. However, if you change alert to eval like so:

function evilEval(stuffToEval)
{
    var ultimateAnswer;

    ultimateAnswer = 42;

    eval(stuffToEval);
}

There are now 3 variables in through. eval, ultimateAnswer and stuffToEval.

This was found and reported here: eslint/eslint#376

[Constellation]

When eval appears, escope mark the scope dynamic. This is because eval can introduce new variable: eval("var i = 20"). So escope takes very conservative analysis on this pattern.

If you would like to ignore eval detection, you can specify options.ignoreEval

[Constellation]

And if you would like to ignore all dynamic scope (with and eval scopes), you can specify options.optimistic.

[ilyavolodin]

Ahh.. thanks for the explanation. One question though. Wouldn't it make sense to leave variables that were declared outside of eval as static? They are already declared, eval might change their value and add new variables, but it will not be able to change the fact that they are declared.