Introduced in ES11, the optional chaining operator (
?.) allows you to access values within a chain of connected objects where a reference or function in the chain could potentially be a nullish value (i.e.
null). It has the following syntax:
obj.value?.prop obj.value?.[expr] obj.array?.[index] obj.method?.(args)
You can use optional chaining when:
- Accessing object properties or calling object methods;
- Accessing properties with an expression using the bracket notation of the property accessor;
- Accessing array items;
- Making function calls.
// ES11+ const name = posts?.?.author?.name; const result = callback?.(); // ...
The expression is evaluated left-to-right, and when/if the left operand evaluates to a nullish value, then the execution of the entire chain is stopped and evaluated to
undefined (i.e. it short-circuit evaluates to
Without optional chaining you would have to check if each reference or function in the chain is a nullish value (which in some cases could mean a lot of nested checks and repetition). For example, one way to do that is using the logical AND operator (
&&) like so:
const name = posts.length && posts && posts.author && posts.author.name ; const result = callback && callback(); // ...
Here, the logical AND operator would return the first falsy value, or the last operand if there's no falsy value.
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