I don't understand at all. I clicked "I don't get it," then put ".arbitrary" in as a selector, and.....a message comes up saying "Wasn't that awesome?" Nothing else happened.
I believe it's a joke. At least I opened these comments thinking it was a joke akin to VanillaJS framework[1]. querySelectorAll returns an empty array if there are no matches, you don't need fancy string messages or errors for that.
> querySelectorAll returns an empty array if there are no matches, you don't need fancy string messages or errors for that.
An empty NodeList[1] to be precise, which is sort of kind of like an array in that it has a length property and you can access its elements with index notation (`nodeList[0]`), but it doesn't inherit from Array.prototype, so it doesn't support methods like `forEach` or `map`.
Indeed. Though still, NodeList has the length property with which you can check for "emptiness" the same as with an array, that's what I meant to say.
Speaking of which, there are few features in ES2015 that make NodeList more palatable:
1. Iterables. NodeList is iterable and you can use, among others, the for..of construction to iterate over its content.
2. There is the Array.from method for turning array-like objects into true arrays. Not much different from our usual method of calling [].slice.call in this particular case, yet it's a bit shorter, standardized, and has a few additional perks, like accepting map function as the second argument.
My best guess is you could raise an error and then you would always know if a selector didn't match.
In jQuery, a selector which doesn't match will evaluate to true, where as .length would be 0. This is a source of bugs, I'm sure, especially for beginners.
[1] http://vanilla-js.com/