CODEWITHSUNDEEP
javascriptreactjs
Arav
Arav

Reputation: 5247

Question Mark in Variable Name

In React custom hook we are returning ordernumber in the below way what does question mark after the variable receipt?.order?.id means in react

export const useTest = props => {
  ...
  return {
    orderTestNumber: receipt?.test?.id
  };
}

Upvotes: 31

Views: 33775

Answers (2)

Zarik
Zarik

Reputation: 143

Just one thing to mention: You can not use the "Optional chaining operator (?.)" on a non-declared root object, but with an undefined root object. For instance, if you are trying to access the properties of a non-declared "obj" object, you will get an error:

console.log(obj?.someProperty);  
**obj is not defined**

But if you have already declared your object and trying to access the property which is Null or undefined, you will get an undefined result :

const obj = {}
console.log(obj?.someProperty);
**undefined**

OCO is handy when you are working with the objects which are dynamically creating properties/assigning values to the properties, and you are not sure about the validation of the property you are trying to access/manipulate.

Upvotes: 6

Jay
Jay

Reputation: 3107

its called Optional chaining (?.)

The optional chaining operator provides a way to simplify accessing values through connected objects when it's possible that a reference or function may be undefined or null.

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Optional_chaining

Upvotes: 35

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