如何在Typescript中对数组使用可选链接? [英] How to use optional chaining with array in Typescript?
问题描述
我正在尝试将可选链接与数组而不是对象一起使用,但不确定如何做到这一点:
I'm trying to use optional chaining with array instead of object but not sure how to do that:
这就是我想要做的 myArray.filter(x => x.testKey === myTestKey)?[0]
.
但是它给出了这样的错误,所以如何在数组中使用它.
But it's giving error like that so how to use it with array.
推荐答案
您需要在?
后面放置.
才能使用可选链接:
You need to put a .
after the ?
to use optional chaining:
myArray.filter(x => x.testKey === myTestKey)?.[0]
仅使用?
会使编译器认为您正在尝试使用条件运算符(然后由于未看到:
而引发错误.稍后)
Using just the ?
alone makes the compiler think you're trying to use the conditional operator (and then it throws an error since it doesn't see a :
later)
可选链接不仅是TypeScript的事情,而且是已完成的提案也使用普通JavaScript .
Optional chaining isn't just a TypeScript thing - it is a finished proposal in plain JavaScript too.
它可以与上述括号符号一起使用,但也可以与点符号属性访问一起使用:
It can be used with bracket notation like above, but it can also be used with dot notation property access:
const obj = {
prop2: {
nested2: 'val2'
}
};
console.log(
obj.prop1?.nested1,
obj.prop2?.nested2
);
并带有函数调用:
const obj = {
fn2: () => console.log('fn2 running')
};
obj.fn1?.();
obj.fn2?.();
这篇关于如何在Typescript中对数组使用可选链接?的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!