with scope, const and var.

Consider the following functions:

function foo() {
  var o = { a: 1 };
  with (o) {
    var a = 2;
  }
  return(o.a);


function bar() {
  var o = { a: 1 };
  with (o) {
    const a = 2;
  }
  return(o.a);
}

Eagle-eyed readers will have noticed that the only difference between the functions foo and bar is the variable declaration inside the with scope.

foo() returns 2.
bar() returns 1.