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133 lines
5.3 KiB
Markdown
133 lines
5.3 KiB
Markdown
# [NWSAPI](http://dperini.github.io/nwsapi/)
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Fast CSS Selectors API Engine
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NWSAPI is the development progress of [NWMATCHER](https://github.com/dperini/nwmatcher) aiming at [Selectors Level 4](https://www.w3.org/TR/selectors-4/) conformance. It has been completely reworked to be easily extended and maintained. It is a right-to-left selector parser and compiler written in pure Javascript with no external dependencies. It was initially thought as a cross browser library to improve event delegation and web page scraping in various frameworks but it has become a popular replacement of the native CSS selection and matching functionality in newer browsers and headless environments.
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It uses [regular expressions](https://en.wikipedia.org/wiki/Regular_expression) to parse CSS selector strings and [metaprogramming](https://en.wikipedia.org/wiki/Metaprogramming) to transforms these selector strings into Javascript function resolvers. This process is executed only once for each selector string allowing memoization of the function resolvers and achieving unmatched performances.
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## Installation
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To include NWSAPI in a standard web page:
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```html
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<script type="text/javascript" src="nwsapi.js"></script>
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```
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To include NWSAPI in a standard web page and automatically replace the native QSA:
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```html
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<script type="text/javascript" src="nwsapi.js" onload="NW.Dom.install()"></script>
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```
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To use NWSAPI with Node.js:
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```
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$ npm install nwsapi
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```
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NWSAPI currently supports browsers (as a global, `NW.Dom`) and headless environments (as a CommonJS module).
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## Supported Selectors
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Here is a list of all the CSS2/CSS3/CSS4 [Supported selectors](https://github.com/dperini/nwsapi/wiki/CSS-supported-selectors).
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## Features and Compliance
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You can read more about NWSAPI [features and compliance](https://github.com/dperini/nwsapi/wiki/Features-and-compliance) on the wiki.
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## API
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### DOM Selection
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#### `ancestor( selector, context, callback )`
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Returns a reference to the nearest ancestor element matching `selector`, starting at `context`. Returns `null` if no element is found. If `callback` is provided, it is invoked for the matched element.
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#### `first( selector, context, callback )`
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Returns a reference to the first element matching `selector`, starting at `context`. Returns `null` if no element matches. If `callback` is provided, it is invoked for the matched element.
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#### `match( selector, element, callback )`
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Returns `true` if `element` matches `selector`, starting at `context`; returns `false` otherwise. If `callback` is provided, it is invoked for the matched element.
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#### `select( selector, context, callback )`
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Returns an array of all the elements matching `selector`, starting at `context`; returns empty `Array` otherwise. If `callback` is provided, it is invoked for each matching element.
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### DOM Helpers
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#### `byId( id, from )`
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Returns a reference to the first element with ID `id`, optionally filtered to descendants of the element `from`.
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#### `byTag( tag, from )`
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Returns an array of elements having the specified tag name `tag`, optionally filtered to descendants of the element `from`.
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#### `byClass( class, from )`
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Returns an array of elements having the specified class name `class`, optionally filtered to descendants of the element `from`.
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### Engine Configuration
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#### `configure( options )`
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The following is the list of currently available configuration options, their default values and descriptions, they are boolean flags that can be set to `true` or `false`:
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* `IDS_DUPES`: true - true to allow using multiple elements having the same id, false to disallow
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* `LIVECACHE`: true - true for caching both results and resolvers, false for caching only resolvers
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* `MIXEDCASE`: true - true to match tag names case insensitive, false to match using case sensitive
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* `LOGERRORS`: true - true to print errors and warnings to the console, false to mute both of them
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### Examples on extending the basic functionalities
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#### `configure( { <configuration-flag>: [ true | false ] } )`
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Disable logging errors/warnings to console, disallow duplicate ids. Example:
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```js
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NW.Dom.configure( { LOGERRORS: false, IDS_DUPES: false } );
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```
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NOTE: NW.Dom.configure() without parameters return the current configuration.
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#### `registerCombinator( symbol, resolver )`
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Registers a new symbol and its matching resolver in the combinators table. Example:
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```js
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NW.Dom.registerCombinator( '^', 'e.parentElement' );
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```
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#### `registerOperator( symbol, resolver )`
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Registers a new symbol and its matching resolver in the attribute operators table. Example:
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```js
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NW.Dom.registerOperator( '!=', { p1: '^', p2: '$', p3: 'false' } );
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```
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#### `registerSelector( name, rexp, func )`
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Registers a new selector, the matching RE and the resolver function, in the selectors table. Example:
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```js
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NW.Dom.registerSelector('Controls', /^\:(control)(.*)/i,
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(function(global) {
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return function(match, source, mode, callback) {
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var status = true;
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source = 'if(/^(button|input|select|textarea)/i.test(e.nodeName)){' + source + '}';
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return { 'source': source, 'status': status };
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};
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})(this));
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```
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