Hoisting
Hoisting is a JavaScript behavior where variable and function declarations are moved to the top of their containing scope during the compilation phase, before code execution. This allows variables and functions to be used before they are declared in the code, though only the declarations are hoisted, not initializations. It's a fundamental concept for understanding JavaScript's execution context and avoiding common bugs.
Developers should learn hoisting to write predictable JavaScript code and debug issues related to variable scope and temporal dead zones. It's essential when working with var, let, const, and function declarations, as it explains why code like 'console.log(x); var x = 5;' outputs undefined instead of throwing an error. Understanding hoisting helps in code reviews, interviews, and optimizing performance by avoiding redeclarations.