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The let Keyword

In JavaScript, the let keyword is used to declare a variable. Unlike var, let provides block-scoping, making it a more modern and flexible choice for variable declaration.

let name = "John";

Here, we use let to declare a variable named name and assign it the value "John". The use of let allows us to confine the variable's scope to the block or statement it is declared in.

Example:

if (true) {
  let age = 20;
  console.log(age); // Output: 20
}

console.log(age); // Error: age is not defined

In this example, the variable age is confined to the if block, and attempting to access it outside the block results in an error.

Benefits of let over var​

  • Block Scoping: Variables declared with let are limited to the block, statement, or expression they are defined in. This helps prevent unintended variable access.

  • No Hoisting Issues: Unlike variables declared with var, variables declared with let are not hoisted to the top of their scope. This eliminates some common pitfalls associated with variable hoisting.

Reassignment with let​

let score = 100;
score = 150; // Valid: score can be reassigned

Using let allows you to reassign values to a variable declared with it. This flexibility makes it suitable for scenarios where the value of a variable may change during the program's execution.

In subsequent chapters, we'll explore more use cases and nuances of using the let keyword in JavaScript.