If you have worked for companies which let you develop yourself inside the company and use new tools, you'll be like a senior developer with life experience at

If you have worked for companies which let you develop yourself inside the company and use new tools, you'll be like a senior developer with life experience at least. Maybe you will be more relaxed to talk about things and can definitely mentor people and take more responsability. You don't need to become a manager, but doing a little bit of architecture and making sure your workplace is fair and nice can take you a long way. 40 isn't that old. It depends though, you could make it look old. Somebody that goes to the gym infrequently and keeps their health above average will probably still be like their 30's, maybe 25(?)'s. It is not so bad. I think by 60's it can get nasty, but by them, you will be stuck with some legacy crap nobody can understand. But there might be 60 year olds doing frontend in vue, why not. You chose if you want to age.