My Favorite Little Operator

May 22, 2024

Sometimes, there are little things that solve so much that we take for granted. There’s also things that solve so much that aren’t used as often.

Recently, I’ve been relying on ??, which is a very interesting operator called “null-coalescing operator”. A fairly seasoned programmer probably uses it very often and wouldn’t find this as fascinating as I did, but for me, it’s a game-changer.

Take this for instance:

const somevar = null;
if (somevar === null) {
    console.log("non-null value");
} else {
    console.log(somevar);
}

Here, we print out somevar, and if it’s null, we print a string. You can also use a ternary operator to clean it up and rewrite it like this.

const somevar = null;
console.log(somevar === null ? "non-null value" : somevar);

But the ?? is much cleaner:

const somevar = null;
console.log(somevar ?? "non-null value");

Pretty neat, eh? Notice how null is not the same as undefined in JS, Dart, C#, etc. So, if I do this in JavaScript

console.log(variablethatdoesntexist ?? "value that does exist");

I get an error.

PHP, as terrible as it may be, has the cool little isset() function, and ?? can be used, not only to check for nullity, but to also see if a value is defined:

print_r($variablethatdoesntexist ?? "value that does exist");

This is perfectly valid PHP code with readability. Whether it’s good practice or not is a different matter of discussion…