Do a Hackathon
As a junior developer, if you want only ONE thing to advance your career -- this is it. Join a hackathon.
First, just to make it clear. In hackathons, people do not break into systems. Quite the opposite -- they build things (which is also called "hacking" -- thank you, English).
"But why a hackathon? I can just build the same thing at home, on my own timeline!"
a) Hackathons give you very different energy -- mostly because you're surrounded by others (see Tip 192). Usually, if you don't have an existing team, you can find teammates at the hackathon start -- and we know that building with others is way more fun (and better learning)!
b) Hackathons are time constrained. A classic hackathon runs 24 hours (fun fact -- a common sponsor for hackathons is Red Bull, you might have an idea why); these are the most intensive building sprints. There are other formats: weekly (start on Monday, build during the week, present on the weekend), even monthly.
c) Usually, there are prizes! Tech companies love sponsoring hackathons (guess why? they hunt for talent!). And having a "hackathon winner" line on your resume is a real prize by itself.
And also, really, it's not an all-or-nothing situation, not at all! Having the "hackathon participant" line on your resume (and the project on your GitHub, see Tip 8) is a real big thing. So, you don't need to be an experienced dev to enjoy the hackathon -- when I judge, often, the most interesting projects are built by juniors!
Now, where to look for hackathons?
I recommend you start by looking at your local tech scene: your university chat, or local meetups are good places to start. Local hackathons have the best energy, and are best for meeting people.
For larger-scale hackathons (mostly online), check out Devpost and MLH.
So, just go ahead, find a hackathon that's happening this month -- and show up!