Blog

In JavaScript, let and var are both used to declare variables, but they have some important differences in terms of scope and behavior.

• The var keyword was used to declare variables before the introduction of let and const in ECMAScript 6 (ES6). Variables declared with var are function-scoped, which means they are only accessible within the function in which they were declared, or if they were declared outside any function, they are accessible throughout the global scope. If a variable is declared with var keyword inside a function, it is still accessible throughout the function, even if it’s declared inside an if-statement or for loop, for example.

function varFunction() {
  if (true) {
    var x = 5;
  }
  console.log(x); // Output: 5
}
varFunction();
console.log(x); // Output: 5

• The let keyword was introduced in ECMAScript 6 (ES6) as an alternative to var, and it is block-scoped. Variables declared with let are only accessible within the block in which they were declared.

function letFunction() {
  if (true) {
    let x = 5;
  }
  console.log(x); // ReferenceError: x is not defined
}
letFunction();