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TODAY I LEARNED

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

Optional Chaining Operator(?) (**)

//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:

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.

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

# => "Exist Ferrari"

Nullish Coalescing Operator(??) (**)

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

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


console.log(car.attributes.model);
# => "Ferrari"

Now the new car object does not have the model property, so we get an undefined value

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

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.

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

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

Learned by leyaim-jimenez on Mar 4, 2021

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