1. Java is extremely versatile and used practically everywhere; JavaScript is primarily used for front-end web development with some traction server-side (Node), mobile-side (React Native), and desktop-side (Electron).
2. Java was a well-designed language; JavaScript was designed in only 10 days and it shows. The latest ECMAScript is pretty much about putting lipstick on a pig.
3. Java is heavily object-oriented; JavaScript is mostly procedural with some support for object-oriented and functional programming.
4. Java uses class-based inheritance; JavaScript uses prototypal inheritance. JavaScript “OOP” is prototype-based.
5. JavaScript has better support for lambdas.
6. Java is statically and strongly typed; JavaScript is dynamically and weakly typed (allowing for all manner of crazy-ass coercions).
7. Java has block-level scoping; JavaScript has function-level scoping.
8. Java has mandatory statement terminators; in JavaScript, they’re optional which can lead to comical situations.
9. Java executes bytecode in a language virtual machine; JavaScript is essentially interpreted (and JIT’d) in the so-called JavaScript engine.
10. Java is backed by the Oracle Corporation (and previously by Sun Microsystems); JavaScript has no corporate sponsorship.
11. There are far more job opportunities for Java than for JavaScript. According to Indeed.com, in the United States at the time of writing, Java has 66,633 job postings, whereas JavaScript has 37,110. Java is better for your career.

Java and JavaScript share only two qualities:

• they both have largely C-like syntax
• they have the first four characters of their names in common

Otherwise, they are completely different languages.