What does the remark "Var statement is not at the scope start" mean about js code?

Question

PyCharm

PyCharm (python development environment) for js code makes a remark in almost every function about incorrect (but not critical) code: "Var statement is not at the scope start". For example in this piece:

$("#Level1").change(function(){
        $('#Level3').children('div').empty();
        var parentKey = $(this).val();
        setLevel2(parentKey);
});

The same, for example, for declaring a counter in an iterator.
What does it mean?