The national average in the U.S for a mid-level front-end developer is around $75k. Of course when you first start expect to enter the field at around 35k depending upon location and portfolio.
Image source: http://intersog.com/blog/chicago-tech-salary-guide-2015/
A lead/senior front-end developer/engineer can potentially live wherever they want (i.e., work remotely) and make over $150k a year (visit angel.co, sign-up, review front-end jobs over $150k or examine the salary ranges on Stack Overflow Jobs).