https://www.getzola.org/search.js

1function debounce(func, wait) {
2  var timeout;
3
4  return function () {
5    var context = this;
6    var args = arguments;
7    clearTimeout(timeout);
8
9    timeout = setTimeout(function () {
10      timeout = null;
11      func.apply(context, args);
12    }, wait);
13  };
14}
15
16// Taken from mdbook
17// The strategy is as follows:
18// First, assign a value to each word in the document:
19//  Words that correspond to search terms (stemmer aware): 40
20//  Normal words: 2
21//  First word in a sentence: 8
22// Then use a sliding window with a constant number of words and count the
23// sum of the values of the words within the window. Then use the window that got the
24// maximum sum. If there are multiple maximas, then get the last one.
25// Enclose the terms in <b>.
26function makeTeaser(body, terms) {
27  var TERM_WEIGHT = 40;
28  var NORMAL_WORD_WEIGHT = 2;
29  var FIRST_WORD_WEIGHT = 8;
30  var TEASER_MAX_WORDS = 30;
31
32  var stemmedTerms = terms.map(function (w) {
33    return elasticlunr.stemmer(w.toLowerCase());
34  });
35  var termFound = false;
36  var index = 0;
37  var weighted = []; // contains elements of ["word", weight, index_in_document]
38
39  // split in sentences, then words
40  var sentences = body.toLowerCase().split(". ");
41
42  for (var i in sentences) {
43    var words = sentences[i].split(" ");
44    var value = FIRST_WORD_WEIGHT;
45
46    for (var j in words) {
47      var word = words[j];
48
49      if (word.length > 0) {
50        for (var k in stemmedTerms) {
51          if (elasticlunr.stemmer(word).startsWith(stemmedTerms[k])) {
52            value = TERM_WEIGHT;
53            termFound = true;
54          }
55        }
56        weighted.push([word, value, index]);
57        value = NORMAL_WORD_WEIGHT;
58      }
59
60      index += word.length;
61      index += 1;  // ' ' or '.' if last word in sentence
62    }
63
64    index += 1;  // because we split at a two-char boundary '. '
65  }
66
67  if (weighted.length === 0) {
68    return body;
69  }
70
71  var windowWeights = [];
72  var windowSize = Math.min(weighted.length, TEASER_MAX_WORDS);
73  // We add a window with all the weights first
74  var curSum = 0;
75  for (var i = 0; i < windowSize; i++) {
76    curSum += weighted[i][1];
77  }
78  windowWeights.push(curSum);
79
80  for (var i = 0; i < weighted.length - windowSize; i++) {
81    curSum -= weighted[i][1];
82    curSum += weighted[i + windowSize][1];
83    windowWeights.push(curSum);
84  }
85
86  // If we didn't find the term, just pick the first window
87  var maxSumIndex = 0;
88  if (termFound) {
89    var maxFound = 0;
90    // backwards
91    for (var i = windowWeights.length - 1; i >= 0; i--) {
92      if (windowWeights[i] > maxFound) {
93        maxFound = windowWeights[i];
94        maxSumIndex = i;
95      }
96    }
97  }
98
99  var teaser = [];
100  var startIndex = weighted[maxSumIndex][2];
101  for (var i = maxSumIndex; i < maxSumIndex + windowSize; i++) {
102    var word = weighted[i];
103    if (startIndex < word[2]) {
104      // missing text from index to start of `word`
105      teaser.push(body.substring(startIndex, word[2]));
106      startIndex = word[2];
107    }
108
109    // add <em/> around search terms
110    if (word[1] === TERM_WEIGHT) {
111      teaser.push("<b>");
112    }
113    startIndex = word[2] + word[0].length;
114    teaser.push(body.substring(word[2], startIndex));
115
116    if (word[1] === TERM_WEIGHT) {
117      teaser.push("</b>");
118    }
119  }
120  teaser.push("…");
121  return teaser.join("");
122}
123
124function formatSearchResultItem(item, terms) {
125  return '<div class="search-results__item">'
126  + `<a href="${item.ref}">${item.doc.title}</a>`
127  + `<div>${makeTeaser(item.doc.body, terms)}</div>`
128  + '</div>';
129}
130
131function initSearch() {
132  var $searchInput = document.getElementById("search");
133  var $searchResults = document.querySelector(".search-results");
134  var $searchResultsItems = document.querySelector(".search-results__items");
135  var MAX_ITEMS = 10;
136
137  var options = {
138    bool: "AND",
139    fields: {
140      title: {boost: 2},
141      body: {boost: 1},
142    }
143  };
144  var currentTerm = "";
145  var index;
146  
147  var initIndex = async function () {
148    if (index === undefined) {
149      index = fetch("/search_index.en.json")
150        .then(
151          async function(response) {
152            return await elasticlunr.Index.load(await response.json());
153        }
154      );
155    }
156    let res = await index;
157    return res;
158  }
159
160  $searchInput.addEventListener("keyup", debounce(async function() {
161    var term = $searchInput.value.trim();
162    if (term === currentTerm) {
163      return;
164    }
165    $searchResults.style.display = term === "" ? "none" : "block";
166    $searchResultsItems.innerHTML = "";
167    currentTerm = term;
168    if (term === "") {
169      return;
170    }
171
172    var results = (await initIndex()).search(term, options);
173    if (results.length === 0) {
174      $searchResults.style.display = "none";
175      return;
176    }
177
178    for (var i = 0; i < Math.min(results.length, MAX_ITEMS); i++) {
179      var item = document.createElement("li");
180      item.innerHTML = formatSearchResultItem(results[i], term.split(" "));
181      $searchResultsItems.appendChild(item);
182    }
183  }, 150));
184
185  window.addEventListener('click', function(e) {
186    if ($searchResults.style.display == "block" && !$searchResults.contains(e.target)) {
187      $searchResults.style.display = "none";
188    }
189  });
190}
191
192
193if (document.readyState === "complete" ||
194    (document.readyState !== "loading" && !document.documentElement.doScroll)
195) {
196  initSearch();
197} else {
198  document.addEventListener("DOMContentLoaded", initSearch);
199}