Local Scope

Local Scope

  • Variables defined inside a function are in the local scope

  • A variable with local scope cannot be referenced outside of that function

  • Functions create their own private scope that prevents code from outside directly accessing it’s variables

Example

function showInspirationalMessage() {
  // "message" variable is declared **inside** a function which means it is LOCAL to this function

  const message = "Don't give up, you can do it!!"
  console.log(message)
}

// prints message variable
showInspirationalMessage()

/*
Now let's attempt to directly access the message variable
and log it out to the console
*/

console.log(message) // <-- Error! The variable is local to the function can cannot be "directly" accessed outside of the function

JS Bin on jsbin.com

  • As you can see in this example any variables declared / defined inside of the showInspirationalMessage() function are only accessible inside showInspirationalMessage; this prevents any other code from outside of the function from directly accessing it’s variables

Local Scope with Parameters

  • Function parameters are local to the function and cannot be accessed outside of the function

Example

function squareMe(number) {
  // The "number" parameter is variable that is LOCAL to the squareMe function

  return number**2
}

const result = squareMe(7)
console.log(result)

/*
Now let's attempt to directly access the `number` parameter
*/

console.log(number) // <-- Error! The variable is local to the function can cannot be "directly" accessed outside of the function

JS Bin on jsbin.com

Variables with the same name in different scopes ARE NOT THE SAME

  • Multiple variables with the same name but different scopes each will be treated as if they are distinct variables with each variable containing their own separate values

Example

// declare a variable named 'actor' in the Global Scope
const actor = "Daniel Craig"

function bestBondActor() {
  // declare a variable named 'actor' within a function (Local Scope)
  const actor  = "Sean Connery"
  return actor
}

const result = bestBondActor()
console.log(result) // <-- prints Sean Connery

/*
Now let's print out the `actor` variable
*/

console.log(actor) // <-- prints Daniel Craig

JS Bin on jsbin.com