Uglify seems to not rewrite object keys which is never exposed publicly. In this example the key "veryLongKeyName" could have been rewritten too something shorter without any danger. Uglify 2.2.1 command used: uglifyjs file.js --output file.min.js --compress dead-code=true,unsafe=true,unused=true --mangle sort=true

uglify_obj_keys.after.js

// After minification
function Foo(){
  var e = {
		veryLongKeyName:!0
	};

	function n(){
		return e.veryLongKeyName
	}

	return{
		publicMethod:function(){
			return n()
		}
	}
}

uglify_obj_keys.before.js

// Before minification
function Foo() {

  var veryLongObjectName = {
		veryLongKeyName : true
	}

	function veryLongFunctionName() {
		return veryLongObjectName.veryLongKeyName;
	}

	return {
		publicMethod : function() {
			return veryLongFunctionName();
		}
	}

}