是否存在反向逻辑零赋值

Question

因此，只有当当前存储的值为零时，??=运算符才会将值分配给变量。

也许我错过了显而易见的东西，但我想不出一个巧妙的解决方案(没有if语句(，只在值不为null时赋值？

我使用nodeJS来提供更多上下文。

---

我想要

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

编辑以更清楚地解决我的问题：

我只希望变量被分配一个新值，如果该新值不是零。

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

Answer 1

不，这不是一个单独的运算符。最接近的是两个运营商：

x = undefined ?? x;

Answer 2

在澄清后添加另一个答案作为编辑我以前的答案似乎很奇怪。

我能想到一个没有if的解决方案的最简单方法如下：

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;

Answer 3

您可以使用逻辑AND赋值。

来自MDN Web文档：

let a = 1;
let b = 0;
a &&= 2;
console.log(a);
// expected output: 2
b &&= 2;
console.log(b);
// expected output: 0