Scope in Block Statements

Scope in Block Statements

  • Block statements like if and switch conditions or for and while loops, unlike functions, will create a new scope if you use let or const but NOT when you use var

Example

  • Declaring a variable within a Block statement using let creates local scope
if (true) {
  // this 'if' conditional block creates a new scope because we use 'let'
  const name = 'Prince' // name is local to the if block
  console.log(name) // logs 'Prince'
}

console.log('----')
console.log(name) // <--- error because the 'name' variable can only be accessed from within the block (due to the use of 'let')

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  • Declaring a variable within a Block statement using var DOES NOT create local scope
if (true) {
  var name = 'Prince' // declare a variable using 'var`
  console.log(name) // logs 'Prince'
}

console.log('----')
console.log(name) // <--- logs 'Prince' because the 'name' variable is in the global scope due to the use of `var`

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