问为什么google闭包编译不将可重用的索引保存在变量中？

EN

var foo = new function() {
  var keyA = 'some-very-long-key';
  var keyB = 'another-key';
  this.bar = function() {
    obj[keyA] = {};
  }
  this.baz = function(data) {
    obj[keyA][keyB] = data;
  }
}();

var foo = new function() {
  this.bar = function() {
    obj["some-very-long-key"] = {};
  };
  this.baz = function(a) {
    obj["some-very-long-key"]["another-key"] = a;
  };
};

var keyA = 'some-very-long-key';
var keyB = 'another-key';
function bar() {
  obj[keyA] = {};
}
function baz(data) {
  obj[keyA][keyB] = data;
}

var keyA = "some-very-long-key", keyB = "another-key";
function bar() {
  obj[keyA] = {};
}
function baz(a) {
  obj[keyA][keyB] = a;
}
;