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Scope defines the accessibility (visibility) of variables. JavaScript variables have three types of scope:
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Before ES6 (2015), JavaScript variables only had Global Scope and Function Scope.
ES6 introduced two important keywords: let and const.
These keywords enable Block Scope in JavaScript.
Variables declared inside a { } block cannot be accessed from outside that block.
| { let x = 2; } // x can NOT be used here |
Variables declared with the var keyword do not have block scope.
Variables declared inside a { } block with var can be accessed from outside the block.
| { var x = 2; } // x CAN be used here |