Tokens parsel.tokenize(selector);
parsel.specificity(selector);
parsel.tokenize(selector);
parsel.parse(selector);
Parsel is an ES module. You import it like so:
import * as parsel from "https://parsel.verou.me/dist/parsel.js"
Note that to use that your script needs to use type="module"
or be imported from a script that does.
If you can't or don't want to use ES modules you can use parsel_nomodule.js
in a regular <script>
tag:
<script src="https://parsel.verou.me/dist/nomodule/parsel.js"></script>
After that, you can use parsel
as a global.
Fun fact: You could also use the module version of Parsel and convert it to a global this way:
<script type="module">
import * as parsel from "https://parsel.verou.me/dist/parsel.js";
window.parsel = parsel;
</script>
Then, assuming your code runs after the DOMContentLoaded
event, you can use the global normally.
In fact, we are assigning parsel
to a global in this very page this way, so you can open your console and play with it!
You can also install via npm: npm install parsel-js
Get list of tokens as a flat array:
parsel.tokenize(selector)
Get AST:
parsel.parse(selector)
You can also provide options:
parsel.parse(selector, {recursive: false, list: false})
The recursive
option parses the arguments of pseudo-classes whose argument is a selector like :not()
, :is()
, :where()
etc into a subtree
property.
The list
option parses selector lists (A, B, C
). The only reason to turn it off is as a performance optimization when you are processing a large volume of selectors that are not lists (e.g. the output of certain CSS parsers like Rework)
Traverse all tokens of a (sub)tree:
parsel.walk(node, callback)
callback
is called with each node as the only argument.
Generate all tokens of a (sub)tree:
parsel.flatten(node)
This can be looped through with for ... of
. Uses the same order as walk
Convert a list of tokens or a (sub)tree to a string:
parsel.stringify(listOrNode)
Calculate specificity (returns an array of 3 numbers):
parsel.specificity(selectorOrNode)
To convert the specificity array to a number, you can use parsel.specificityToNumber(specificity [, base])
.
If a base is not provided, it will be the max specificity component + 1.
Try it out! In this page, parsel
is assigned to a global so you can experiment with the API in the console!
You can import TOKENS
and add new types.
All values need to be regular expression objects with the global flag on.
For example, to add the nesting selector:
parsel.TOKENS.nesting = /&/g;
Do note that this way, new tokens are added to the end of the object literal.
You may want to add tokens before other tokens, e.g. to add support for @nest
.
This is a little tricky, because you cannot just replace the object literal with another,
so the only way to add a property after another property is to delete all properties after that property, add your new property, then re-add them.
So, to add support for @nest
, we need to add it before the type
token, since @nest
tokens are currently incorrectly parsed as type
tokens.
Since type
is the very last token, we only need to delete and re-add that:
// Delete property type
let temp = {};
temp.type = parsel.TOKENS.type;
delete parsel.TOKENS.type;
// Add new token
parsel.TOKENS.nest = /@nest\b/g;
// Re-add type
parsel.TOKENS.type = temp.type;
This can get tedious, so you can use a helper function for that:
function insert(obj, {before, property, value}) {
let found, temp = {};
for (let p in obj) {
if (p === before) {
found = true;
}
if (found) {
temp[p] = obj[p];
delete obj[p];
}
}
Object.assign(obj, {property: value, ...temp});
}
Then you can do:
insert(parsel.TOKENS, {before: "type", property: "nest", value: /@nest\b/g});
For convenience, you can also find this helper function in insert.js
, and you can just import it:
import insert from "./parsel/insert.js";
insert(parsel.TOKENS, {before: "type", property: "nest", value: /@nest\b/g});
There are also some alternative implementations of this helper available.