Does Typescript support the ?. operator? (And, what's it called?)

Question

Does Typescript currently (or are there plans to) support the safe navigation operator of ?.

ie:

var thing = foo?.bar // same as: var thing = (foo) ? foo.bar : null; 

Also, is there a more common name for this operator (it's incedibly hard to google for).

Answer 1

Yes. As of TypeScript 3.7 (released on November 5, 2019), this feature is supported and is called Optional Chaining:

At its core, optional chaining lets us write code where TypeScript can immediately stop running some expressions if we run into a null or undefined. The star of the show in optional chaining is the new ?. operator for optional property accesses.

Refer to the TypeScript 3.7 release notes for more details.

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Prior to version 3.7, this was not supported in TypeScript, although it was requested as early as Issue #16 on the TypeScript repo (dating back to 2014).

As far as what to call this operator, there doesn't appear to be a consensus. In addition to "optional chaining" (which is also what it's called in JavaScript), there are a couple of other examples:

• CoffeeScript refers to it as the existential operator (specifically, the "accessor variant" of the existential operator):

The accessor variant of the existential operator ?. can be used to soak up null references in a chain of properties. Use it instead of the dot accessor . in cases where the base value may be null or undefined.

• C# calls this a null-conditional operator.

a null-conditional operator applies a member access, ?., or element access, ?[], operation to its operand only if that operand evaluates to non-null; otherwise, it returns null.

• Kotlin refers to it as the safe call operator.

There are probably lots of other examples, too.

Answer 2

It is now possible, see answer of user "Donut".

Old answer: Standard JavaScript behaviour regarding boolean operators has something that may help. The boolean methods do not return true or false when comparing objects, but in case of OR the first value that is equal to true.

Not as nice as a single ?, but it works:

var thing = foo && foo.bar || null; 

You can use as many && as you like:

var thing = foo && foo.bar && foo.bar.check && foo.bar.check.x || null; 

Default values are also possible:

var name = person && person.name || "Unknown user";