The problem with hiring junior developers is risk. They could be junior because of incompetence or wrong attitude opposed to just lacking necessary experience. When hiring a junior you are hedging either competence or experience against expenses and hoping for potential. Potential is the magical ingredient and its hard to recognize before hiring somebody, which is why this is risky.
Conversely hiring really good seniors saves the company money even if a good senior is really expensive. A good senior can probably do the work of 4 junior developers while also introducing code that demands less maintenance into the future, which pay dividends over time.
What I see from some juniors who spoil it for everybody else is immaturity and unrealistic expectations. A hiring company is there to provide you compensation for work. They aren't there to satisfy some emotional fantasy or other self-serving justification.
Because there is greater risk in hiring juniors demand for juniors is lower and there are more juniors competing for those fewer positions.
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With all of that said above, the goal isn't to get a better junior job, but rather become a senior. Here is how I did it.
First of all I didn't want to be a developer. Travelocity couldn't hire competent front-end developers. It's like they didn't exist. The company saw potential in me and involuntarily relocated me into a developer position. If I wanted to stay employed I had to figure it out. I sucked really bad a first and felt like I was struggling in a vacuum.
After about a year of this my military job needed me to perform security assessments in Afghanistan. You have a tremendous amount of available time on military deployments. Just before deploying I started a personal project, which I continue to work on today nearly a decade later. This little code beautification project kept me busy and it forced me into deep learning of complex algorithms.
When you are deployed in a combat zone you have to be self-sufficient. You don't often have internet. At the time I was writing code on a small netbook with 16gb total storage, because it was durable and portable. I didn't carry around a bunch of unnecessary tooling. You simply learn to do more with less.
Once I got back to Travelocity I discovered I had surpassed some of my peers in problem solving and code proficiency. I was coding all the time even when I didn't have to. I had found every little bit of proficiency I had gained in personal practice allowed me to work faster which then allowed me to become that much more proficient like an accelerating force.
The primary distinguishing factor between seniors and juniors to me is self-sufficiency, predictability, and simplicity. I find juniors tend to spend most of their time living in frameworks, dependency nonsense, tooling, and configurations. These external things distract from predictability and simplicity. They certainly don't benefit self-sufficiency.