In order to get out of this availability and compatibility problem, there are a couple of transpilers that you can use. Transpilers take your original ES8 code, and transform it into equivalent JS5 code. (It's a source-to-source transformation, instead of a source-to-object code as in compilation.) You can code using advanced ES8 features, but the user's browsers will receive JS5 code. A transpiler will also let you keep up with upcoming versions of the language, despite the time needed by browsers to adopt new standards across desktop and mobile devices.
If you wonder where did the word transpiler come from, it is a portmanteau of translate and compiler. There are many such combinations in technological speak: email (electronic+mail), ...
