robots-txt-parser

A lightweight robots.txt parser for Node.js with support for wildcards, caching and promises.

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robots-txt-parser
Coverage Status npm version npm A lightweight robots.txt parser for Node.js with support for wildcards, caching and promises.

Installing

Via NPM: npm install robots-txt-parser --save.

Getting Started

After installing robots-txt-parser it needs to be required and initialised: ```js const robotsParser = require('robots-txt-parser'); const robots = robotsParser( { 
userAgent: 'Googlebot', // The default user agent to use when looking for allow/disallow rules, if this agent isn't listed in the active robots.txt, we use *.
allowOnNeutral: false // The value to use when the robots.txt rule's for allow and disallow are balanced on whether a link can be crawled.
}); ``` Example Usage: ```js const robotsParser = require('robots-txt-parser'); const robots = robotsParser( { 
userAgent: 'Googlebot', // The default user agent to use when looking for allow/disallow rules, if this agent isn't listed in the active robots.txt, we use *.
allowOnNeutral: false, // The value to use when the robots.txt rule's for allow and disallow are balanced on whether a link can be crawled.
}, ); robots.useRobotsFor('http://example.com') .then(() => { 
robots.canCrawlSync('http://example.com/news'); // Returns true if the link can be crawled, false if not.
robots.canCrawl('http://example.com/news', (value) => {
console.log('Crawlable: ', value);
}); // Calls the callback with true if the link is crawlable, false if not.
robots.canCrawl('http://example.com/news') // If no callback is provided, returns a promise which resolves with true if the link is crawlable, false if not.
.then((value) => {
console.log('Crawlable: ', value);
});
}); ```

Condensed Documentation

Below is a condensed form of the documentation, each is a function that can be found on the robotsParser object. | Method | Parameters | Return | | ----------- | -------- | ------ | | parseRobots(key, string) | key:String, string:String | None | | isCached(domain) | domain:String | Boolean for whether robots.txt for url is cached. | | fetch(url) | url:String | Promise, resolved when robots.txt retrieved. | | useRobotsFor(url) | url:String | Promise, resolved when robots.txt is fetched. | | canCrawl(url)| url:String, callback:Func (Opt) | Promise, resolves with Boolean. | | getSitemaps()| callback:Func (Opt) | Promise if no callback provided, resolves with String. | | getCrawlDelay() | callback:Func (Opt) | Promise if no callback provided, resolves with Number. | | getCrawlableLinks(links) | links:[String], callback:Func (Opt) | Promise if no callback provided, resolves with String. | | getPreferredHost() | callback:Func (Opt) | Promise if no callback provided, resolves with String. | | setUserAgent(userAgent) | userAgent:String | None. | | setAllowOnNeutral(allow) | allow:Boolean | None. | | clearCache() | None | None. |

Full Documentation

---

parseRobots

robots.parseRobots(key, string) Parses a string representation of a robots.txt file and cache's it with the given key.
Parameters
  • key -> Can be any URL.
  • string -> String representation of a robots.txt file.
Returns
None.
Example
```js robots.parseRobots('https://example.com', ` 
User-agent: *
Allow: /*.php$
Disallow: /
`); ``` ---

isCached

robots.isCached(domain) A method used to check if a robots.txt has already been fetched and parsed.
Parameters
  • domain -> Can be any URL.
Returns
Returns true if a robots.txt has already been fetched and cached by the robots-txt-parser.
Example
```js robots.isCached('https://example.com'); // true or false robots.isCached('example.com'); // Attempts to check the cache for only http:// and returns true or false. ``` ---

fetch

robots.fetch(url) Attempts to fetch and parse a robots.txt file located at the url, this method avoids checking the built-in cache and will always attempt to retrieve a fresh copy of the robots.txt.
Parameters
  • url -> Any URL.
Returns
Returns a Promise which will resolve once the robots.txt has been fetched with the parsed robots.txt.
Example
```js robots.fetch('https://example.com/robots.txt') 
.then((tree) => {
console.log(Object.keys(tree)); // Will log sitemap and any user agents.
});
``` ---

useRobotsFor

robots.useRobotsFor(url) Attempts to download and use the robots.txt at the given url, if the robots.txt has already been downloaded, reads from the cached copy instead.
Parameters
  • url -> Any URL.
Returns
Returns a promsise that resolves once the URL is fetched and parsed.
Example
```js robots.useRobotsFor('https://example.com/news') 
.then(() => {
// Logic to check if links are crawlable.
});
``` ---

canCrawl

robots.canCrawl(url, callback) Tests whether a url can be crawled for the current active robots.txt and user agent. If a robots.txt isn't cached for the domain of the url, it is fetched and parsed before returning a boolean value.
Parameters
  • url -> Any URL.
  • callback -> An optional callback, if undefined returns a promise.
Returns
Returns a Promise which will resolve with a boolean value.
Example
```js robots.canCrawl('https://example.com/news') 
.then((crawlable) => {
console.log(crawlable); // Will log a boolean value.
});
``` ---

getSitemaps

robots.getSitemaps(callback) Returns a list of sitemaps present on the active robots.txt.
Parameters
  • callback -> An optional callback, if undefined returns a promise.
Returns
Returns a Promise which will resolve with an array of strings.
Example
```js robots.getSitemaps() 
.then((sitemaps) => {
console.log(sitemaps); // Will log an list of strings.
});
``` ---

getCrawlDelay

robots.getCrawlDelay(callback) Returns the crawl delay on requests to the current active robots.txt.
Parameters
  • callback -> An optional callback, if undefined returns a promise.
Returns
Returns a Promise which will resolve with an Integer.
Example
```js robots.getCrawlDelay() 
.then((crawlDelay) => {
console.log(crawlDelay); // Will be an Integer greater than or equal to 0.
});
``` ---

getCrawlableLinks

robots.getCrawlableLinks(links, callback) Takes an array of links and returns an array of links which are crawlable for the current active robots.txt.
Parameters
  • links -> An array of links to check for crawlability.
  • callback -> An optional callback, if undefined returns a promise.
Returns
A Promise that will resolve to contain an Array of all the crawlable links.
Example
```js robots.getCrawlableLinks() 
.then((links) => {
console.log(links);
});
``` ---

getPreferredHost

robots.getPreferredHost(callback) Returns the preferred host name specified in the active robots.txt's host: directive or null if there isn't one.
Parameters
  • callback -> An optional callback, if undefined returns a promise.
Returns
An String if the host is defined, undefined otherwise.
Example
```js robots.getPreferredHost() 
.then((host) => {
console.log(host);
});
``` ---

setUserAgent

robots.setUserAgent(userAgent) Sets the current user agent to use when checking if a link can be crawled.
Parameters
  • userAgent -> A string.
Returns
undefined
Example
```js robots.setUserAgent('exampleBot'); // When interacting with the robots.txt we now look for records for 'exampleBot'. robots.setUserAgent('testBot'); // When interacting with the robots.txt we now look for records for 'testBot'. ``` ---

setAllowOnNeutral

robots.setAllowOnNeutral(allow) Sets the canCrawl behaviour to return true or false when the robots.txt rules are balanced on whether a link should be crawled or not.
Parameters
  • allow -> A boolean value.
Returns
undefined
Example
```js robots.setAllowOnNeutral(true); // If the allow/disallow rules are balanced, canCrawl returns true. robots.setAllowOnNeutral(false); // If the allow/disallow rules are balanced, canCrawl returns false. ``` ---

clearCache

robots.clearCache() The cache can get extremely long over extended crawling, this simple method resets the cache.
Parameters
None
Returns
None
Example
```js robots.clearCache(); ``` ---

Synchronous API

Synchronous variants of the API, will be deprecated in a future version.

canCrawlSync

robots.canCrawlSync(url) Tests whether a url can be crawled for the current active robots.txt and user agent. This won't attempt to fetch the robots.txt if it is not cached.
Parameters
  • url -> Any url.
Returns
Returns a boolean value depending on whether the url is crawlable. If there is no cached robots.txt for this url, it will always return true.
Example
```js robots.canCrawlSync('https://example.com/news') // true or false. ``` ---

getSitemapsSync()

robots.getSitemapsSync() Returns a list of sitemaps present on the active robots.txt.
Parameters
None
Returns
An Array of Strings.
Example
```js robots.getSitemapsSync(); // Will be an array e.g. 'http://example.com/sitemap1.xml', 'http://example.com/sitemap2.xml'. ``` ---

getCrawlDelaySync()

robots.getCrawlDelaySync() Returns the crawl delay on specified in the active robots.txt's for the active user agent
Parameters
None
Returns
An Integer greater than or equal to 0.
Example
```js robots.getCrawlDelaySync(); // Will be an Integer. ``` ---

getCrawlableLinksSync

robots.getCrawlableLinksSync(links) Takes an array of links and returns an array of links which are crawlable for the current active robots.txt.
Parameters
  • links -> An array of links to check for crawlability.
Returns
An Array of all the links are crawlable.
Example
```js robots.getCrawlableLinks('example.com/test/news', 'example.com/test/news/article'); // Will return an array of the links that can be crawled. ``` ---

getPreferredHostSync

robots.getPreferredHostSync() Returns the preferred host name specified in the active robots.txt's host: directive or undefined if there isn't one.
Parameters
None
Returns
An String if the host is defined, undefined otherwise.
Example
```js robots.getPreferredHostSync(); // Will be a string if the host directive is defined . ```
License
See LICENSE file.
Resources
Robots.txt Specifications by Google A Standard for Robot Exclusion Robots.txt Specifications by Yandex