- Understanding of scope
- Concurrency model and the event loop
- Regular expression
- Memory management
Closure is created when an inner function has access to its outer function variables and arguments. The inner function can access three scope chains: Its variables; Outer function’s variables and arguments; Global variables. For example, an outer function has a variable a, and returns the inner function, which utilizes this outer variable. Inner functions have access to its parent scope, even after the parent function has been executed.
Global variables can be accessed and modified anywhere in the program, while local variables can be accessed only inside the function declaration. Variables declared without a var keyword inside any function becomes global variables automatically.
The garbage collection algorithms rely on the concept of reference. This supposedly automatic resource freeing gives developers the false impression they can choose not to care about memory management. Global variables, forgotten timers and closures are common root causes of memory leaks
Know the whole ecosystem of software development
Managing JS frameworks
Depending on the project status and existing team you may already have all technology stack chosen, otherwise you may want to look for a Senior JS developer to build your project from scratch.
A middle JS programmer should be able to work effectively with the existing tools and frameworks on the project. If you decide to hire a junior coder, make sure that the candidate has experience of working with your current tech stack.
Other Crucial Skills for a JS Programmer
- Debugging and testing frameworks
- Task runners and module bundlers
- Tools for managing asynchronous code
- Code linters and formatters
- Tools for working with Networking and HTTP-based APIs
- Package managers
Besides this, developers should know how to work with the browser API, to be able to store data on the client, manipulate data, etc. Some projects may require visual representation with graphs or producing dynamic, interactive data visualizations, so your developers should have experience with such libraries as D3.js, Highcharts, Chart.js.
Building JS developers team