Null coalescing operator in React JS/ Typescript

Question

We have the Null coalescing operator in .NET and we can use as below

string postal_code = address?.postal_code;

Same thing can we do in React JS?

What i found like we can do with && operator

in address.ts file

string postal_code = address && address.postal_code;

what i need like .net feature is possible in typescript with react JS, is that possible ?

something like:

string postal_code = address?.postal_code // I am getting the error in this line if I try to use like .NET

Solution 1

This is a proposed feature in TypeScript, under the legendary Issue #16

It won't be introduced into TypeScript until the ECMAScript spec for this feature is firm as there is a desire for the TypeScript implementation to follow that specification - so you'll get it early, but not massively early in this case.

It is referred to as any of the following:

• Null Propagation Operator
• Existential Operator
• Null Coalesce Operator

Solution 2

Update in 2020: The nullish-coalescing operator mentioned below is now through the process and in ES2020, as is the optional chaining operator that lets you do:

let postal_code = address?.postal_code;
// −−−−−−−−−−−−−−−−−−−−−−^

With optional chaining, if address is null or undefined, postal_code will get undefined as its value. But if address is neither null nor undefined, postal_code will get the value of address.postal_code.

---

JavaScript doesn't have a null-coalescing operator (nor does TypeScript, which mostly limits itself to adding a type layer and adopting features that are reasonably far along the path to making it into JavaScript). There is a proposal for a JavaScript null-coalescing operator, but it's only at Stage 1 of the process.

Using the && idiom you've described is a fairly common approach:

let postal_code = address && address.postal_code;

If address is null (or any other falsy¹ value), postal_code will be that same value; otherwise, it will be whatever value address.postal_code was.

---

¹ The falsy values are 0, "", NaN, null, undefined, and of course false.

Comments

[Trevor]

Any update on this? Looks like the issue is still locked. Also, are there any efficient workarounds for the time being?

[Dave]

The "null coalesce" operator is the related-but-different ?? operator. Also both of these proposals recently went to stage 2, so hopefully it will be implemented soon!