That option may have become available some time ago, but I haven't looked at Polymer in quite awhile. Two-way binding can be a great and convenient thing, but having it as the only option, in the early days of Polymer, led to many headaches (for me, at least). The reason is that two-way binding can make it practically impossible to reason deterministically about data flow when several or more bindings come into play.
https://www.polymer-project.org/1.0/docs/devguide/data-bindi...
That option may have become available some time ago, but I haven't looked at Polymer in quite awhile. Two-way binding can be a great and convenient thing, but having it as the only option, in the early days of Polymer, led to many headaches (for me, at least). The reason is that two-way binding can make it practically impossible to reason deterministically about data flow when several or more bindings come into play.