identify/lib/identify.js

Generate id attributes for HTML block elements

'use strict';

// Generate `id` attributes for HTML block elements.
// Copyright 2012 Tom Vincent <http://tlvince.com/contact>
// <https://github.com/tlvince/identify.js>

// DOM selectors and general heavy lifting
var cheerio = require('cheerio');

// Big list of HTML(5) block elements.
//
// From: [Mozilla Developer Network][1].
// [1]: https://developer.mozilla.org/en-US/docs/HTML/Block-level_elements
var blockElements = [
  'address',
  'article',
  'aside',
  'audio',
  'blockquote',
  'canvas',
  'dd',
  'div',
  'dl',
  'fieldset',
  'figcaption',
  'figure',
  'footer',
  'form',
  'h1',
  'h2',
  'h3',
  'h4',
  'h5',
  'h6',
  'header',
  'hgroup',
  'hr',
  'noscript',
  'ol',
  'output',
  'p',
  'pre',
  'section',
  'table',
  'tfoot',
  'ul',
  'video'
];

// Default options
var defaults = {
  blockElements: blockElements,
  anchor: false
};

// Sanitise a given string
//
// Performs the following transformations (in order):
//
//   * Replace ampersand with 'and'
//   * Replace one or more spaces or commars with a dash
//   * Filter non alphanumerics and dashes
//   * Flatten a series of two or more dashes
//   * Strip leading/trailing dash
//
// `words` - The number of words to return.
//
//  Returns the sanitised string
var sanitise = function(str, words) {
  if (words === null) {
    words = 0;
  }
  str = str.toLowerCase();
  if (words > 0) {
    str = str.split(' ').slice(0, +(words - 1) + 1 || 9e9).toString();
  }
  str = str.replace(/&/g, 'and');
  str = str.replace(/(\s+|,+)/g, '-');
  str = str.replace(/[^a-z0-9-]/g, '');
  str = str.replace(/-{2,}/g, '-');
  str = str.replace(/(^-|-$)/, '');
  return str;
};

// Add id attributes to block elements in the given HTML.
//
// Does not clobber existing attributes.
//
// Returns the processed HTML.
var identify = function(html, _options) {
  var $ = cheerio.load(html, {
    lowerCaseTags: true
  });

  var options = defaults;
  for (var k in _options) {
    options[k] = _options[k];
  }

  var i, len;
  for (i = 0, len = options.blockElements.length; i < len; i++) {
    var tag = options.blockElements[i];
    // jshint loopfunc: true
    $(tag).each(function(index) {
      var id = $(this).attr('id');
      if (!id) {
        switch (tag) {
        case 'h1':
        case 'h2':
        case 'h3':
        case 'h4':
        case 'h5':
        case 'h6':
          id = sanitise($(this).text());
          break;
        case 'p':
          id = sanitise($(this).text(), 3);
          break;
        default:
          id = tag + (index + 1);
        }
        $(this).attr('id', id);
      }
      if (options.anchor) {
        $(this).prepend('<a href="#' + id + '" class="anchor"></a>');
      }
    });
  }
  return $.html();
};

module.exports = identify;