JSHint considers a for-in variable 'bad'. What does this mean?

Question

The following code:

var things = {'foo':'bar'}
for ( thing in things ) {
  console.log(thing)
}

Consistently produces the following error in jshint:

Bad for in variable 'thing'.

I do not understand what makes the 'thing' variable 'bad' - as you can see, it is not being used anywhere else. What should I do differently to make jshint not consider this to be an error?

Answer 1

They always are - if they are not declared. Try adding var if thing has not been previously declared.

for ( var thing in things ) {
  console.log(thing)
}

or

var thing;

//more code

for ( thing in things ) {
  console.log(thing)
}