Scope refers to the visibility and accessibility of variables and functions in a particular part of a program.
JavaScript has function-level scope, which means that variables and functions defined inside a function are only accessible within that function.
This concept is known as lexical scoping, where the scope of a variable is determined by its position within the source code.
In addition to function-level scope, JavaScript also has global scope, which means that variables and functions defined outside of any function are accessible globally.
Global variables and functions can be accessed from anywhere in the program, which can lead to potential naming conflicts and other issues.
ES6 introduced block-level scope with the 'let' and 'const' keywords, which allows variables to be scoped to the block in which they are defined, such as a loop or an if statement.
Overall, understanding scope is important for writing clean and maintainable JavaScript code, as it helps prevent variable name collisions and other scope-related issues.