freeCodeCamp/guide/english/certifications/javascript-algorithms-and-data-structures/object-oriented-programming/use-closure-to-protect-properties-within-an-object-from-being-modified-externally/index.md

---
title: Use Closure to Protect Properties Within an Object from Being Modified Externally
---
## Use Closure to Protect Properties Within an Object from Being Modified Externally

### Method

Just like in the example given, rather than declaring the `weight` variable with the `this` keyword, the `let` keyword must be used to declare it as a private variable. This way it can only be accessed inside the `Bird` function. The `getWeight` method must then be added inside the `Bird` function to access the `weight` variable. 

### Solution

```javascript

function Bird() {
  let weight = 15;
  
  this.getWeight = function() {
    return weight;
  };
  
}

```

### Solution 2

In ES6 syntax we can make the function a bit less verbose:

```
function Bird() {
  let weight = 15;
  this.getWeight = () => weight;  
}
```