Lecture 190:- Closures and let

In JavaScript, closures can be created by functions that are defined inside other functions. A closure is created when a function returns another function and that returned function uses variables from its parent scope. These variables are stored in the closure, and they can be accessed by the returned function even after the parent function has finished executing.

In terms of the difference between let and var in closures, the use of let can help prevent some common issues that may arise with closures and var. For example, if you use var in a closure, the variable declared with var is hoisted to the top of the function, and any changes made to that variable inside the closure will be reflected outside the closure as well. This can be confusing and lead to unexpected behavior.

Using let instead of var in closures can help avoid this issue. When you declare a variable with let in a closure, it is not hoisted to the top of the function, and any changes made to that variable inside the closure will not be reflected outside the closure. This can help make your code more predictable and easier to debug.

Here's an example of using let in a closure:

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function createCounter() {  let count = 0;  return function() {    count++;    console.log(count);  } } const counter = createCounter(); counter(); // logs 1 counter(); // logs 2 counter(); // logs 3

In this example, createCounter() returns a function that increments and logs a count variable. Because count is declared with let, it is not hoisted to the top of the function, and the closure maintains its own copy of the count variable. This allows the counter function to increment and log the count variable without affecting any other code outside of the closure.