Duplicate variable creation in JavaScript - Is it problematic?

Question

I've noticed Photoshop's ScriptListener code kick out a duplicate line.

    var idChnl = charIDToTypeID( "Chnl" );
    var idChnl = charIDToTypeID( "Chnl" );

This ScriptListener bug aside, my question is this: Is it problematic, when a variable in a script, (such as idChnl), is created twice?

Answer 1

The second variable assignment (or if more than two variable assignments, the last variable assignment) will overwrite the initial assignment(s) as seen in this example:

var a = "Hello";
var a = "World";

alert(a);

With regards to problems with this, code readability and confusion with code maintenance in the long run are a few of the problems I could think of.