varscope

varscope.js

function invalid(a) {
  var inner = function() {
    console.log(a);
    
    var a = '2';
    
    console.log(a);
  }
  
  inner();
}
 
function valid(b) {
  var inner = function() {
    console.log(b);
    
    var a = '2';
    
    console.log(a);
  }
  
  inner();
}
 
/**
 * invalid('1') ->
 *  'undefined'
 *  '2'
 *
 * valid('1') ->
 *  '1'
 *  '2'
 * 
 * Is this expected behaviour or a bug?
 */