robots-txt-parser

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:

1const robotsParser = require('robots-txt-parser');
2const robots = robotsParser(
3  {
4    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 *.
5    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.
6  });

Example Usage:

1const robotsParser = require('robots-txt-parser');
2
3const robots = robotsParser(
4  {
5    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 *.
6    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.
7  },
8);
9
10robots.useRobotsFor('http://example.com')
11  .then(() => {
12    robots.canCrawlSync('http://example.com/news'); // Returns true if the link can be crawled, false if not.
13    robots.canCrawl('http://example.com/news', (value) => {
14      console.log('Crawlable: ', value);
15    }); // Calls the callback with true if the link is crawlable, false if not.
16    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.
17      .then((value) => {
18        console.log('Crawlable: ', value);
19      });
20  });

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

1robots.parseRobots('https://example.com',
2  `
3   User-agent: *
4   Allow: /*.php$
5   Disallow: /
6  `);

---

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

1robots.isCached('https://example.com'); // true or false
2robots.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

1robots.fetch('https://example.com/robots.txt')
2    .then((tree) => {
3        console.log(Object.keys(tree)); // Will log sitemap and any user agents.
4    });

---

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

1robots.useRobotsFor('https://example.com/news')
2    .then(() => {
3        // Logic to check if links are crawlable.
4    });

---

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

1robots.canCrawl('https://example.com/news')
2    .then((crawlable) => {
3        console.log(crawlable); // Will log a boolean value.
4    });

---

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

1robots.getSitemaps()
2    .then((sitemaps) => {
3        console.log(sitemaps); // Will log an list of strings.
4    });

---

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

1robots.getCrawlDelay()
2    .then((crawlDelay) => {
3        console.log(crawlDelay); // Will be an Integer greater than or equal to 0.
4    });

---

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

1robots.getCrawlableLinks([])
2    .then((links) => {
3        console.log(links);
4    });

---

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

1robots.getPreferredHost()
2    .then((host) => {
3        console.log(host);
4    });

---

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

1robots.setUserAgent('exampleBot'); // When interacting with the robots.txt we now look for records for 'exampleBot'.
2robots.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

1robots.setAllowOnNeutral(true); // If the allow/disallow rules are balanced, canCrawl returns true.
2robots.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

1robots.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

1robots.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

1robots.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

1robots.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

1robots.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

1robots.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