Vivienne Reay

Block Scoping

Block scoping refers to the way variables are scoped within a block of code, typically defined by a pair of curly braces {}. Prior to the introduction of ECMAScript 6 (ES6), JavaScript had function-level scoping, meaning that variables declared inside a function were only accessible within that function.

With the introduction of the let and const keywords in ES6, JavaScript gained block-scoping capabilities. Variables declared with let and const are scoped to the nearest enclosing block, which can be a statement or a set of curly braces.

var teacher = "Kyle";

{
  let teacher = "Suzy";
  console.log(teacher); // Suzy
}

console.log(teacher); // Kyle

• var teacher = "Kyle"; declares a variable teacher in the global scope and assigns the value "Kyle" to it.
• {} defines a block. Inside this block, let teacher = "Suzy"; declares a new variable teacher that is block-scoped to the curly braces. This teacher variable has a local scope within the block and does not affect the value of the global teacher.
• console.log(teacher); inside the block logs the value of the block-scoped teacher, which is "Suzy."
• console.log(teacher); outside the block logs the value of the global teacher, which is "Kyle."