Optional chaining

This is an experimental technology
Check the Browser compatibility table carefully before using this in production.

The optional chaining operator ?. permits reading the value of a property located deep within a chain of connected objects without having to expressly validate that each reference in the chain is valid. The ?. operator functions similarly to the . chaining operator, except that instead of causing an error if a reference is nullish (null or undefined), the expression short-circuits with a return value of undefined. When used with function calls, it returns undefined if the given function does not exist.

This results in shorter and simpler expressions when accessing chained properties when the possibility exists that a reference may be missing. It can also be helpful while exploring the content of an object when there's no known guarantee as to which properties are required.

Syntax

obj?.prop
obj?.[expr]
arr?.[index]
func?.(args)

Description

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.

For example, consider an object obj which has a nested structure. Without optional chaining, looking up a deeply-nested subproperty requires validating the references in between, such as:

let nestedProp = obj.first && obj.first.second;

The value of obj.first is confirmed to be non-null (and non-undefined) before then accessing the value of obj.first.second. This prevents the error that would occur if you simply accessed obj.first.second directly without testing obj.first.

With the optional chaining operator (?.), however, you don't have to explicitly test and short-circuit based on the state of obj.first before trying to access obj.first.second:

let nestedProp = obj.first?.second;

By using the ?. operator instead of just ., JavaScript knows to implicitly check to be sure obj.first is not null or undefined before attempting to access obj.first.second. If obj.first is null or undefined, the expression automatically short-circuits, returning undefined.

This is equivalent to the following:

let nestedProp = ((obj.first === null || obj.first === undefined) ? undefined : obj.first.second);

Optional chaining with function calls

You can use optional chaining when attempting to call a method which may not exist. This can be helpful, for example, when using an API in which a method might be unavailable, either due to the age of the implementation or because of a feature which isn't available on the user's device.

Using optional chaining with function calls causes the expression to automatically return undefined instead of throwing an exception if the method isn't found:

let result = someInterface.customMethod?.();

Note: If there is a property with such a name and which is not a function, using ?. will still raise a TypeError exception (x.y is not a function).

Dealing with optional callbacks or event handlers

If you use callbacks or fetch methods from an object with a destructuring assignment, you may have non-existent values that you cannot call as functions unless you have tested their existence. Using ?., you can avoid this extra test:

// Written as of ES2019
function doSomething(onContent, onError) {
  try {
    // ... do something with the data 
  }
  catch (err) {
    if (onError) { // Testing if onError really exists
      onError(err.message);
    }
  }
}
// Using optional chaining with function calls
function doSomething(onContent, onError) {
  try {
   // ... do something with the data
  }
  catch (err) {
    onError?.(err.message); // no exception if onError is undefined
  }
}

Optional chaining with expressions

You can also use the optional chaining operator when accessing properties with an expression using the bracket notation of the property accessor:

let nestedProp = obj?.['prop' + 'Name'];

Array item access with optional chaining

let arrayItem = arr?.[42];

Examples

Basic example

This example looks for the value of the name property for the member bar in a map when there is no such member. The result is therefore undefined.

let myMap = new Map();
myMap.set("foo", {name: "baz", desc: "inga"});

let nameBar = myMap.get("bar")?.name;

Short-circuiting evaluation

When using optional chaining with expressions, if the left operand is null or undefined, the expression will not be evaluated. For instance:

let potentiallyNullObj = null;
let x = 0;
let prop = potentiallyNullObj?.[x++];

console.log(x); // 0 as x was not incremented

Stacking the optional chaining operator

With nested structures, it is possible to use optional chaining multiple times:

let customer = {
  name: "Carl",
  details: {
    age: 82,
    location: "Paradise Falls" // detailed address is unknown
  }
};
let customerCity = customer.details?.address?.city;

// … this also works with optional chaining function call
let duration = vacations.trip?.getTime?.();

Combining with the nullish coalescing operator

The nullish coalescing operator may be used after optional chaining in order to build a default value when none was found:

let customer = {
  name: "Carl",
  details: { age: 82 }
};
const customerCity = customer?.city ?? "Unknown city";
console.log(customerCity); // Unknown city

Specifications

Specification Status Comment
Proposal for the "optional chaining" operator Stage 3

Browser compatibility

Update compatibility data on GitHub
DesktopMobileServer
ChromeEdgeFirefoxInternet ExplorerOperaSafariAndroid webviewChrome for AndroidFirefox for AndroidOpera for AndroidSafari on iOSSamsung InternetNode.js
Optional chaining operator (?.)
Experimental
Chrome Full support 79
Disabled
Full support 79
Disabled
Disabled From version 79: this feature is behind the Experimental JavaScript preference (needs to be set to true). To change preferences in Chrome, visit chrome://flags.
Edge No support NoFirefox No support NoIE No support NoOpera Full support 65
Disabled
Full support 65
Disabled
Disabled From version 65: this feature is behind the Experimental JavaScript preference (needs to be set to true).
Safari No support NoWebView Android No support NoChrome Android Full support 79
Disabled
Full support 79
Disabled
Disabled From version 79: this feature is behind the Experimental JavaScript preference (needs to be set to true). To change preferences in Chrome, visit chrome://flags.
Firefox Android No support NoOpera Android No support NoSafari iOS No support NoSamsung Internet Android No support Nonodejs No support No

Legend

Full support  
Full support
No support  
No support
Experimental. Expect behavior to change in the future.
Experimental. Expect behavior to change in the future.
User must explicitly enable this feature.
User must explicitly enable this feature.

Implementation Progress

The following table provides a daily implementation status for this feature, because this feature has not yet reached cross-browser stability. The data is generated by running the relevant feature tests in Test262, the standard test suite of JavaScript, in the nightly build, or latest release of each browser's JavaScript engine.

See also