# Question 44

### Question

Can you explain how JavaScript determines the value of `this` in nested functions?

### Answer

`this` in nested functions is determined by several factors working together. It's all about **lexical scoping** and **how execution context is set up**.

Here's the breakdown:

1. **Lexical Scope:** JavaScript looks for `this` value based on where the function was *defined*, not where it's *called*. This is why it's often said that `this` is determined by lexical scoping.
2. **Execution Context Stack:** Each time a function is called, a new execution context is created and pushed onto a stack. The top of the stack determines the current context and therefore the value of `this`.

**Scenario 1: Regular Function Calls**

```javascript
function outer() {
  const value = 'hello'; // This is part of the outer function's scope

  function inner() {
    console.log(this); // In this case, 'this' refers to the global object (window in browsers)
  }

  inner(); 
}

outer(); 
```

**Explanation:**

* `this` inside `inner()` is bound to the **global object** because it's a regular function call.

**Scenario 2: Nested Function Calls with Contextual Binding**

```javascript
const obj = {
  value: 'world', // Property of the object
  outer: function() {
    function inner() {
      console.log(this); // 'this' refers to the object (obj) itself
    }
    inner(); 
  }
};

obj.outer();
```

**Explanation:**

* `this` inside `inner()` is bound to the **object (`obj`)** on which the `outer` method was called. This happens because of lexical scoping and how `inner`'s context inherits from `outer`.

**Key Points:**

* The **lexical scope** (where a function is defined) determines the initial binding of `this`.
* However, **contextual binding** can override the default value of `this`, for example, with functions like `call()`, `apply()`, or `bind()`.