It is usually more susceptible to bugs than the back end. The combination of a lack of control over the environment your code runs in and javascript's weak typing give it that extra dose of fun.
In the same vein as your comment, I might as well say back end development sucks because the default MySQL datastore quietly drops strings longer than the field[1].
These days front-end =/= Javascript[2] by a long shot (maybe yours is, but blame the person who made that decision for your project).
1. I don't know if that's still true. If it is, then I'm glad I no longer have to deal with MySQL.
2. GWT had strong-typing since forever. Not that I'm endorsing it, but it's still front end. I do recommend TypeScript
> the default MySQL datastore quietly drops strings longer than the field [...] I don't know if that's still true. If it is, then I'm glad I no longer have to deal with MySQL.
That's still true, as I recall. To avoid this nonsense, you need to change the sql_mode - either globally in the server config, or only within your session by issuing an SQL query.
Yes. A lot of back-end devs would rather chew glass than debug for four browsers, plus mobile devices.