Optional Chaining Operator (?) and Nullish Coalescing Operator (??) 

Optional Chaining Operator(?) (**)

```javascript
//Car object
const car = {
  attributes: {
   year: 2021,
   model: "Ferrari"
  }
}
```
Before in javascript to validate that the attributes of an object exist, it was necessary to use the `And operator (&&)` to validate if the attributes of the object existed.

See the following example:

```javascript
if (car && car.attributes && car.attributes.model) {
  console.log('Exist',  car.attributes.model)
} else {
  console.log('Do not exist')
}

# => "Exist Ferrari"
```
Now with `Optional Chaining Operator (?)` We can validate if the property exit will return undefined if the property attributes or model doesn’t exist.

```javascript
if (car?.attributes?.model) {
  console.log('Exist',  car.attributes.model)
} else {
  console.log('Do not exist')
}

# => "Exist Ferrari"
```

Nullish Coalescing Operator(??) (**)

```javascript
//Car object
const car = {
  attributes: {
   year: 2021,
   model: "Ferrari"
  }
}
```

If we want to get the car model then we would like below:

```javascript

console.log(car.attributes.model);
# => "Ferrari"
```
Now the new car object does not have the model property, so we get an undefined value

```javascript
//Car object
const car = {
  attributes: {
   year: 2021,
  }
}
```

```javascript
console.log(car.attributes.model);
# => "undefined"
```

To avoid the undefined value the  ` OR (| |)` operator can be used, It will now return the value BMW because the property model is undefined. But what if the name property is empty like below example

```javascript
console.log(car.attributes.model | | "BMW" );
# => "BMW"
```

Now the problem is when the property model exists but has an empty, undefined or null value we will get the BMW value and this is not right. 

```javascript
//Car object
const car = {
  attributes: {
   year: 2021,
   model: ""
  }
}
```

```javascript
console.log(car.attributes.model | | "BMW" );
# => "BMW"
```

The solution for this problem is to use the Nullish Coalescing Operator (??), Which will print the result as an empty string.

```javascript
console.log(car.attributes.model ?? "BMW" );
# => ""
```

leyaim-jimenez
March 4, 2021