Parse Github `Links` header in JavaScript

gistfile1.js

/*
 * parse_link_header()
 *
 * Parse the Github Link HTTP header used for pageination
 * http://developer.github.com/v3/#pagination
 */
function parse_link_header(header) {
  if (header.length == 0) {
    throw new Error("input must not be of zero length");
  }

  // Split parts by comma
  var parts = header.split(',');
  var links = {};
  // Parse each part into a named link
  _.each(parts, function(p) {
    var section = p.split(';');
    if (section.length != 2) {
      throw new Error("section could not be split on ';'");
    }
    var url = section[0].replace(/<(.*)>/, '$1').trim();
    var name = section[1].replace(/rel="(.*)"/, '$1').trim();
    links[name] = url;
  });

  return links;
}

Do you know if this can be used for parsing general (non gh specific) link headers?

No, this code won't work for headers with links that contain , or ;.

FOR THOSE WHO NEED IT WITHOUT JQUERY

function parse_link_header(header) {
if (header.length == 0) {
throw new Error("input must not be of zero length");
}

// Split parts by comma
var parts = header.split(',');
var links = {};
// Parse each part into a named link
for(i=0;i<parts.length;i++)
{
var section = parts[i].split(';');
if (section.length != 2) {
throw new Error("section could not be split on ';'");
}
var url = section[0].replace(/<(.)>/, '$1').trim();
var name = section[1].replace(/rel="(.)"/, '$1').trim();
links[name] = url;
}

return links;
}

Put @Gilmargolin 's code inside a code block for readability and fixed it up. No jquery or underscore here.

function parse_link_header(header) {
    if (header.length === 0) {
        throw new Error("input must not be of zero length");
    }

    // Split parts by comma
    var parts = header.split(',');
    var links = {};
    // Parse each part into a named link
    for(var i=0; i<parts.length; i++) {
        var section = parts[i].split(';');
        if (section.length !== 2) {
            throw new Error("section could not be split on ';'");
        }
        var url = section[0].replace(/<(.*)>/, '$1').trim();
        var name = section[1].replace(/rel="(.*)"/, '$1').trim();
        links[name] = url;
    }
    return links;
}

If someone needs this the PHP way...:

function parseLinkHeader($header) {
    if (strlen($header) == 0) {
        throw new \Exception("input must not be of zero length");
    }

    $parts = explode(',', $header);
    $links = [];

    foreach($parts as $p) {
        $section = explode(';', $p);
        if (count($section) != 2) {
            throw new \Exception("section could not be split on ';'");
        }
        $url = trim(preg_replace("/<(.*)>/", '$1', $section[0]));
        $name = trim(preg_replace("/rel=\"(.*)\"/", '$1', $section[1]));
        $links[$name] = $url;
    }
    return $links;
}

parse_link_header doesn't work with:

'<http://mementoweb.org/wikipedia/>;rel="original", <http://mementoarchive.lanl.gov/twa/memento/20130919212835/http://mementoweb.org/wikipedia/>;rel="memento"; datetime="Thu, 19 Sep 2013 21:28:35 GMT", <http://mementoarchive.lanl.gov/twa/memento/20160920160128/http://mementoweb.org/wikipedia/>;rel="memento last"; datetime="Tue, 20 Sep 2016 16:01:28 GMT", <http://mementoarchive.lanl.gov/twa/memento/20130912190257/http://mementoweb.org/wikipedia/>;rel="memento first"; datetime="Thu, 12 Sep 2013 19:02:57 GMT", <http://mementoarchive.lanl.gov/twa/memento/20130919220632/http://mementoweb.org/wikipedia/>;rel="memento next"; datetime="Thu, 19 Sep 2013 22:06:32 GMT", <http://mementoarchive.lanl.gov/twa/memento/20130919212641/http://mementoweb.org/wikipedia/>;rel="memento prev"; datetime="Thu, 19 Sep 2013 21:26:41 GMT" , <http://mementoarchive.lanl.gov/twa/timemap/link/http://mementoweb.org/wikipedia/>;rel="timemap"; type="application/link-format" , <http://mementoarchive.lanl.gov/twa/timegate/http://mementoweb.org/wikipedia/>;rel="timegate"'.

I'm using parse-link-header.

Handle the comma inside quotes with lookahead/lookbehind (only works on JS engines that support it)

function parseLinkHeader(header) {
    if (header.length === 0) {
        throw new Error("input must not be of zero length");
    }

    // Split parts by comma and parse each part into a named link
    return header.split(/(?!\B"[^"]*),(?![^"]*"\B)/).reduce((links, part) => {
        const section = part.split(/(?!\B"[^"]*);(?![^"]*"\B)/);
        if (section.length < 2) {
            throw new Error("section could not be split on ';'");
        }
        const url = section[0].replace(/<(.*)>/, '$1').trim();
        const name = section[1].replace(/rel="(.*)"/, '$1').trim();

        links[name] = url;

        return links;
    }, {});
}

Can't it be as simple as?

function parseLink(s) {
  const output = {};
  const regex = /<([^>]+)>; rel="([^"]+)"/g;

  let m;
  while (m = regex.exec(s)) {
    const [_, v, k] = m;
    output[k] = v;
  }

  return output;
}

Usage: parseLink(headers.get("link"))

There is a package for this github-parse-link

Lodash:

const links = _.chain(link)
        .split(',')
        .map(link => {
          return {
            ref: link.split(';')[1].replace(/rel="(.*)"/, '$1').trim(),
            url: link.split(';')[0].replace(/<(.*)>/, '$1').trim(),
          }
        })
        .keyBy('ref')
        .mapValues('url')
        .value()