People on twitter loved this trick I learned from a coworker's pull request the other day. You might like it too.
TIL this works #javascript pic.twitter.com/l4wtDypkC5
— Swizec Teller (@Swizec) April 20, 2022
You can use ?.() to call a potentially undefined function 🤯 Works for array access too. ?.[]
The common use case for optional chaining is object access. If you're like me, that gave you the wrong mental model of the operator.
const bird = {
name: "Kiwi",
species: ["Parrot"],
}
// prints undefined
console.log(user.address?.street)
If . is chaining, then ? is the optional part. Obvious.
And wrong. ?. is the optional chaining operator for JavaScript.
That gives you the flexibility to use it anywhere. Function calls, array access, ... I can't think of others.
Optional chaining doesn't guarantee that what you're using supports the way you're holding it. Optional chaining is not a type check, it's an ergonomic way to hold null and undefined values.
Best used in combination with TypeScript, which guarantees (ish) the correct type of underlying value. Like this:
type Bird = {
name: string
species?: string[]
address?: {
continent: string
environment: string
}
}
const BirdButton = (props: { bird: Bird; onClick?: Function }) => {
const { bird, onClick } = props
return (
<button onClick={() => onClick?.()}>
{bird.name} is a {bird.species?.[0]} from the {bird.address?.environment}{" "}
of {bird.address?.continent}
</button>
)
}
The ? in TypeScript types means "possibly undefined". The ?. in JavaScript lets you use that ergonomically. No more onClick && onClick() 😍
You can use <BirdButton> all these ways:
<BirdButton bird={{ name: "Kiwi" }} />
<BirdButton bird={{ name: "Kiwi" }} onClick={() => alert("hai")} />
<BirdButton bird={{ name: "Kiwi", species: ["Parrot", "Conure"] }} />
<BirdButton
bird={{
name: "Kiwi",
species: ["Parrot", "Conure"],
address: { continent: "Brazil", environment: "Jungle" },
}}
/>
Browser and server environment support is good except you need the latest Safari and recent NodeJS.
Not a concern, if you're using a build step in your code like Babel or TSC. Make sure you regularly update your browserlist because I hear Babel turns ?. into lots of code.
Cheers,
~Swizec
PS: yes my example doesn't do well with partial bird info. It prints Kiwi is a from the of. But that's not the point of this email 😅
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