Key Concepts

Review core concepts you need to learn to master this subject

Scope

Block Scoped Variables

Global Variables

Scope

function myFunction() {
  
  var pizzaName = "Volvo";
  // Code here can use pizzaName
  
}

// Code here can't use pizzaName

Scope is a concept that refers to where values and functions can be accessed.

Various scopes include:

  • Global scope (a value/function in the global scope can be used anywhere in the entire program)
  • File or module scope (the value/function can only be accessed from within the file)
  • Function scope (only visible within the function),
  • Code block scope (only visible within a { ... } codeblock)
Scope
Lesson 1 of 1
  1. 1
    Scope
    An important idea in programming is scope. Scope defines where variables can be accessed or referenced. While some variables can be accessed from anywhere within a program, other variables may on…
    Start
  2. 2
    Blocks and Scope
    Before we talk more about scope, we first need to talk about blocks. We’ve seen blocks used before in functions and if statements. A block is the code found inside a set of curly braces {}. Blo…
    Start
  3. 3
    Global Scope
    Scope is the context in which our variables are declared. We think about scope in relation to blocks because variables can exist either outside of or within these blocks. In global scope, varia…
    Start
  4. 4
    Block Scope
    The next context we’ll cover is block scope. When a variable is defined inside a block, it is only accessible to the code within the curly braces {}. We say that variable has block scope becaus…
    Start
  5. 5
    Scope Pollution
    It may seem like a great idea to always make your variables accessible, but having too many global variables can cause problems in a program. When you declare global variables, they go to the _gl…
    Start
  6. 6
    Practice Good Scoping
    Given the challenges with global variables and scope pollution, we should follow best practices for scoping our variables as tightly as possible using block scope. Tightly scoping your variables …
    Start
  7. 7
    Review: Scope
    In this lesson, you learned about scope and how it impacts the accessibility of different variables. Let’s review the following terms: - Scope is the idea in programming that some variables a…
    Start

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