It's unclear from what you just said whether it would consist of just one algorithm problem, or whether it would consist of one algorithm problem and then other questions about frameworks.
Algorithms generally means data structures and algorithms. Stuff like hash tables, sorting, linked lists, binary search, trees, tree traversal methods, runtime complexity. Despite what it sounds like, this is considered basic data structures and algorithms, material that can be covered in one CS class. It's material you could learn through self-study over the course of a month.
For front end developers frameworks/stack/communication probably means questions involving basic knowledge of jQuery and how the DOM works. Also might include questions about anything you list on your resume (e.g. if you list Backbone.js on your resume you might expect questions about Backbone's MVC system, events, etc.). Also might ask you non-coding 'architectural' questions where they ask you to describe in broad terms how you would construct something.
It probably be more would one algorithm problem and then other questions about frameworks.
Yeah good chance a lot of questions on technical ideation and architecturing maybe a very open question, answered whichever tech language I prefer, or in plain english if it has to be cited in a language I am not familiar with.
Since they want to see how you communicate, you should also improve your technical communication skills. How, I don't know.
You should consider studying basic algorithms and data structures. I don't know what resource are out there. There are some MOOCs, and you could use HNSearch to see what people have recommended before.
Algorithms generally means data structures and algorithms. Stuff like hash tables, sorting, linked lists, binary search, trees, tree traversal methods, runtime complexity. Despite what it sounds like, this is considered basic data structures and algorithms, material that can be covered in one CS class. It's material you could learn through self-study over the course of a month.
For front end developers frameworks/stack/communication probably means questions involving basic knowledge of jQuery and how the DOM works. Also might include questions about anything you list on your resume (e.g. if you list Backbone.js on your resume you might expect questions about Backbone's MVC system, events, etc.). Also might ask you non-coding 'architectural' questions where they ask you to describe in broad terms how you would construct something.