var someFunkyVariable = 5;


/// hundreds of lines later
someFunkYVariable = 10;

// hundreds of lines later
if(someFunkyVariable == 5)
{
    CrashAndDeleteRootUser();
}

will throw a script error at the second definition:

Line 5, column 3:  Unqualified assignments are not supported anymore. Use `var` or `const var` or `reg` for definition

. This will help to avoid nasty bugs which are extremely annoying to track down (plus enforce a better coding style). This however is not standard Javascript behaviour (but there is a dialect of Javascript called "strict" Javascript which does the same thing.

One caveat is that the standard for loop syntax

also throws an error message, because i = 0 is a unqualified definition. The solution is to just define i once (or as local variable to be 100% thread-safe):

var i = 0;

for(i = 0; i < 200; i++)
    doSomething();


for(i = 375; i < 500; i++)
    doSomethingElse();


inline function runsOnThreadOne()
{
    // Using local variables makes sure that the iterator value is not
    // changed by the other thread
    local i = 0;

    for(i = 0; i < 200; i++)
        doSomething();
};

inline function runsOnThreadTwo()
{
    local i = 0;

    for(i = 0; i < 200; i++)
        doSomethingElse()
};

I also removed the new operator because it seducts people to use the weirder parts of the Javascript language.