首先检查一个有效的 output（非空），然后使用它多次的最短方法是什么？

Question

Using vanilla js, I've put together a one liner that takes a long function, first checks to see if it has a valid value (not null), and if it has a valid value to use that long function several times in a shortened manner.

The code for it is something like this:

(x => {if (!x) return; x.style.color='brown'; x.style.fontWeight='600';})(document.evaluate('//ul[@class="main-menu"]//li[text()="About"]', document, null, 9).singleNodeValue;);

The html it might work on would be something like this:

<ul class="main-menu">
  <li>Home</li>
  <li>About</li>
</ul>

The long way of doing it would be something like this:

var x = document.evaluate('//ul[@class="main-menu"]//li[text()="About"]', document, null, 9).singleNodeValue;
if (x) {
  x.style.color='brown';
  x.style.fontWeight='600';
}

My final code is actually more like this:

const $e = (xpath) => { return document.evaluate(xpath, document, null, 9).singleNodeValue; }
(x => {if (!x) return; x.style.color='blue'; x.style.fontWeight='900';})($e('//ul[@class="main-menu"]//li[text()="Home"]'));
(x => {if (!x) return; x.style.color='brown'; x.style.fontWeight='600';})($e('//ul[@class="main-menu"]//li[text()="About"]'));

While I worked hard to make these one liners, I feel I could do something better.
I leave this to the gurus to see if this can be improved upon please.
If not, I'll just run with what I have, it seems to work...

The requirements are:

1. One LONG function needs to be put in only ONCE... preferably an Xpath, but any function should do.
2. The output of that function needs to be checked and valid before continuing. (not false, not null)
3. The LONG function can be used several times, in a shortened manner, if output is valid.
4. One line if possible. More than 80 characters is 'okay', but not much more.
5. Unfortunately, this needs to be done in vanilla javascript.
6. I would prefer to not have to declare any variables.

Thanks. Enjoy. I look forward to any answers.

Answer 1

I found that Optional Chaining is the best method for me to go with my specific needs.

$e('//ul[@class="main-menu"]//li[text()="Home"]')?.style.color='blue';

Thanks for watching, wish someone could have suggested it.
I'd thought this could have been a fun one for folks.