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# What is a closure

A closure in JavaScript is a function that has access to the variables in its outer (enclosing) function's scope even after the outer function has returned. This is possible because the inner function maintains a reference to the environment in which it was created, which includes the variables of the outer function.

Here is an example of a closure in JavaScript:

```javascript
function outerFunction() {
  let outerVariable = 'I am the outer variable';

  return function innerFunction() {
    console.log(outerVariable);
  }
}

let closure = outerFunction();
closure(); // logs 'I am the outer variable'
```

In this example, the `innerFunction` has access to the `outerVariable` variable even after the `outerFunction` has returned. This is because the `innerFunction` maintains a reference to the environment in which it was created, which includes the `outerVariable` variable. When we call the `closure` function, it logs the value of `outerVariable`.

Closures are often used to create private variables in JavaScript. They can also be used to create higher-order functions, which are functions that take other functions as arguments or return functions as their result.