So the ??= operator assigns the value to the variable only if the current stored value is nullish.
Maybe I'm missing the obvious but I can't think of a slick solution (without if statements) to only assign if the value is not nullish?
I'm using nodeJS to give a bit more context.
I want
let x r??= 2;
// Updates 'x' to hold this new value
x r??= undefined;
// Has no effect, since the value to assign is nullish
console.log(x); // 2
EDIT to give more clarity to my problem:
I want a variable only to be assigned a new value, if that new value is not nullish.
let iceCream = {
flavor: 'chocolate'
}
const foo = 2.5
const bar = undefined;
iceCream.price r??= bar
// does not assign the new value because it is nullish
console.log(iceCream.price) // expected to be error, no such property
iceCream.price r??= foo
// assigns the new value because it is not nullish but a float
console.log(iceCream.price) // expected to be 2.5
iceCream.price r??= bar
// does not assign the new value because it is nullish
console.log(iceCream.price) // expected to still be 2.5
No, that’s not a single operator. The closest is two operators:
x = undefined ?? x;
Adding another answer after clarification as editing my previous one seemed weird.
The simplest way I can think of a solution without if is as follows:
let iceCream = {
flavor: 'chocolate'
}
const foo = 2.5
const bar = undefined;
bar && (iceCream.price = bar)
// Another possible solution if creating the property with a nullish value is ok for you:
iceCream.price = bar || iceCream.price;
You could use logical AND assignment.
From the MDN Web Docs:
let a = 1;
let b = 0;
a &&= 2;
console.log(a);
// expected output: 2
b &&= 2;
console.log(b);
// expected output: 0