css-select
Advanced tools
Package description
The css-select package is a CSS selector engine that enables querying and manipulating HTML and XML documents using CSS selectors. It can be used to select elements from a DOM tree, similar to how you would select elements in the browser using CSS.
Selecting elements
This feature allows you to select elements from a DOM tree using CSS selectors. The code sample demonstrates selecting all <p> elements from a given HTML string.
const cssSelect = require('css-select');
const parseHTML = require('htmlparser2').parseDocument;
const dom = parseHTML('<div><p>Hello World</p></div>');
const elems = cssSelect('p', dom);
console.log(elems[0].children[0].data); // 'Hello World'Matching elements
This feature checks if a given element matches a CSS selector. The code sample demonstrates checking if the first child of the root element has a class 'foo'.
const cssSelect = require('css-select');
const parseHTML = require('htmlparser2').parseDocument;
const dom = parseHTML('<div class='foo'><p>Hello World</p></div>');
const isMatch = cssSelect.is(dom.children[0], '.foo');
console.log(isMatch); // truePseudo-selectors
This feature allows the use of pseudo-selectors to select elements. The code sample demonstrates selecting the first child of a list.
const cssSelect = require('css-select');
const parseHTML = require('htmlparser2').parseDocument;
const dom = parseHTML('<ul><li>Item 1</li><li>Item 2</li></ul>');
const firstItem = cssSelect(':first-child', dom);
console.log(firstItem[0].children[0].data); // 'Item 1'Cheerio is a fast, flexible, and lean implementation of core jQuery designed specifically for the server. It uses css-select under the hood for its CSS selector engine, providing a familiar jQuery-like API for manipulating the DOM.
jsdom is a pure-JavaScript implementation of many web standards, notably the WHATWG DOM and HTML Standards, for use with Node.js. It allows you to create a DOM from an HTML string and then interact with it as if you were in the browser, including using CSS selectors to find elements.
Soupselect is a module that ports the functionality of Python's BeautifulSoup library to Node.js. It allows for similar CSS selector-based element selection but is less actively maintained and has fewer features compared to css-select.
Readme
a CSS selector compiler/engine
css-select turns CSS selectors into functions that tests if elements match them. When searching for elements, testing is executed "from the top", similar to how browsers execute CSS selectors.
In its default configuration, css-select queries the DOM structure of the
domhandler module (also known as
htmlparser2 DOM). It uses domutils as its
default adapter over the DOM structure. See Options below for details on
querying alternative DOM structures.
Features:
The traditional approach of executing CSS selectors, named left-to-right
execution, is to execute every component of the selector in order, from left to
right (duh). The execution of the selector a b for example will first query
for a elements, then search these for b elements. (That's the approach of
eg. Sizzle,
nwmatcher and
qwery.)
While this works, it has some downsides: Children of as will be checked
multiple times; first, to check if they are also as, then, for every superior
a once, if they are bs. Using
Big O notation, that would be
O(n^(k+1)), where k is the number of descendant selectors (that's the space
in the example above).
The far more efficient approach is to first look for b elements, then check if
they have superior a elements: Using big O notation again, that would be
O(n). That's called right-to-left execution.
And that's what css-select does – and why it's quite performant.
By building a stack of functions.
Wait, what?
Okay, so let's suppose we want to compile the selector a b again, for
right-to-left execution. We start by parsing the selector, which means we turn
the selector into an array of the building-blocks of the selector, so we can
distinguish them easily. That's what the
css-what module is for, if you want to
have a look.
Anyway, after parsing, we end up with an array like this one:
[
{ type: "tag", name: "a" },
{ type: "descendant" },
{ type: "tag", name: "b" },
];
Actually, this array is wrapped in another array, but that's another story (involving commas in selectors).
Now that we know the meaning of every part of the selector, we can compile it. That's where it becomes interesting.
The basic idea is to turn every part of the selector into a function, which takes an element as its only argument. The function checks whether a passed element matches its part of the selector: If it does, the element is passed to the next turned-into-a-function part of the selector, which does the same. If an element is accepted by all parts of the selector, it matches the selector and double rainbow ALL THE WAY.
As said before, we want to do right-to-left execution with all the big O
improvements nonsense, so elements are passed from the rightmost part of the
selector (b in our example) to the leftmost (which would be of course
ca).
//TODO: More in-depth description. Implementation details. Build a spaceship.
const CSSselect = require("css-select");
Note: css-select throws errors when invalid selectors are passed to it, contrary to the behavior in browsers, which swallow them. This is done to aid with writing css selectors, but can be unexpected when processing arbitrary strings.
CSSselect.selectAll(query, elems, options)Queries elems, returns an array containing all matches.
query can be either a CSS selector or a function.elems can be either an array of elements, or a single element. If it is an
element, its children will be queried.options is described below.Aliases: default export, CSSselect.iterate(query, elems).
CSSselect.compile(query, options)Compiles the query, returns a function.
CSSselect.is(elem, query, options)Tests whether or not an element is matched by query. query can be either a
CSS selector or a function.
CSSselect.selectOne(query, elems, options)Arguments are the same as for CSSselect.selectAll(query, elems). Only returns
the first match, or null if there was no match.
All options are optional.
xmlMode: When enabled, tag names will be case-sensitive. Default: false.rootFunc: The last function in the stack, will be called with the last
element that's looked at.adapter: The adapter to use when interacting with the backing DOM
structure. By default it uses the domutils module.context: The context of the current query. Used to limit the scope of
searches. Can be matched directly using the :scope pseudo-selector.cacheResults: Allow css-select to cache results for some selectors,
sometimes greatly improving querying performance. Disable this if your
document can change in between queries with the same compiled selector.
Default: true.A custom adapter must match the interface described here.
You may want to have a look at domutils to
see the default implementation, or at
css-select-browser-adapter
for an implementation backed by the DOM.
As defined by CSS 4 and / or jQuery.
,)*)<tagname>) )>)<)+)~)[attr=foo]), with supported comparisons:
[attr] (existential)=~=|=*=^=$=!=i can be added after the comparison to make the comparison
case-insensitive (eg. [attr=foo i]):not:contains:icontains (case-insensitive version of :contains):has:root:empty:parent:first-child,
:last-child,
:first-of-type,
:last-of-type:only-of-type,
:only-child:nth-child,
:nth-last-child,
:nth-of-type,
:nth-last-of-type,:link,
:any-link:visited,
:hover,
:active
(these depend on optional Adapter methods, so these will only match
elements if implemented in Adapter):selected,
:checked:enabled,
:disabled:required,
:optional:header,
:button,
:input,
:text,
:checkbox,
:file,
:password,
:reset,
:radio etc.:is, plus its
legacy alias :matches:scope
(uses the context from the passed options)License: BSD-2-Clause
To report a security vulnerability, please use the Tidelift security contact. Tidelift will coordinate the fix and disclosure.
css-select for enterpriseAvailable as part of the Tidelift Subscription
The maintainers of css-select and thousands of other packages are working with
Tidelift to deliver commercial support and maintenance for the open source
dependencies you use to build your applications. Save time, reduce risk, and
improve code health, while paying the maintainers of the exact dependencies you
use.
Learn more.
FAQs
a CSS selector compiler/engine
The npm package css-select receives a total of 25,274,216 weekly downloads. As such, css-select popularity was classified as popular.
We found that css-select demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 2 open source maintainers collaborating on the project.
Did you know?
Socket for GitHub automatically highlights issues in each pull request and monitors the health of all your open source dependencies. Discover the contents of your packages and block harmful activity before you install or update your dependencies.
Security News
Tea.xyz, a crypto project aimed at rewarding open source contributions, is once again facing backlash due to an influx of spam packages flooding public package registries.
Security News
As cyber threats become more autonomous, AI-powered defenses are crucial for businesses to stay ahead of attackers who can exploit software vulnerabilities at scale.
Security News
UnitedHealth Group disclosed that the ransomware attack on Change Healthcare compromised protected health information for millions in the U.S., with estimated costs to the company expected to reach $1 billion.