Easy Client-side JavaScript Search With Lunr.js
Search is a must-have for any website or application. A simple search widget can allow users to comb through your entire blog. Or allow customers to browse your inventory. Building a custom photo gallery? Add a search box. Website search functionality is available from a variety of third-party vendors. Or you can take the DIY approach and build the entire backend to answer search API calls.
Lunr.js works on the client-side via JavaScript. Instead of sending calls to a backend, Lunr looks up search terms in an index built on the client-side itself. This avoids expensive back-and-forth network calls between the browser and your server. There are plenty of tutorials online to showcase Lunrâs website search functionality. But you can actually use Lunr.js to search any array of JavaScript objects.
In this how-to, Iâll build a search index for the top 100 books of all time. After that, Iâll show you how to pre-build the index for faster indexing. Iâll also show you how to make the most of Lunrâs search options. And finally, Iâll show off findmymastodon.com – a real-world implementation of Lunr.
Getting Started With Lunr.js
Create a new HTML page called lunr.html. Weâll use this file throughout this guide. At the top of lunr.html, call the main Lunr JS library.
<script src="https://unpkg.com/lunr/lunr.js"></script>
Note: You can find the complete code here.
Loading the Dataset
Next, create a variable called my_big_json. This variable will contain the JSON-ified string of our main dataset. Define the variable in lunr.html within <script> tags.
var my_big_json = '[{"author":"Chinua Achebe","country":"Nigeria","imageLink":"images/things-fall-apart.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Things_Fall_Apart","pages":209,"title":"Things Fall Apart","year":1958},{"author":"Hans Christian Andersen","country":"Denmark","imageLink":"images/fairy-tales.jpg","language":"Danish","link":"https://en.wikipedia.org/wiki/Fairy_Tales_Told_for_Children._First_Collection.","pages":784,"title":"Fairy tales","year":1836},{"author":"Dante Alighieri","country":"Italy","imageLink":"images/the-divine-comedy.jpg","language":"Italian","link":"https://en.wikipedia.org/wiki/Divine_Comedy","pages":928,"title":"The Divine Comedy","year":1315},{"author":"Unknown","country":"Sumer and Akkadian Empire","imageLink":"images/the-epic-of-gilgamesh.jpg","language":"Akkadian","link":"https://en.wikipedia.org/wiki/Epic_of_Gilgamesh","pages":160,"title":"The Epic Of Gilgamesh","year":-1700},{"author":"Unknown","country":"Achaemenid Empire","imageLink":"images/the-book-of-job.jpg","language":"Hebrew","link":"https://en.wikipedia.org/wiki/Book_of_Job","pages":176,"title":"The Book Of Job","year":-600},{"author":"Unknown","country":"India/Iran/Iraq/Egypt/Tajikistan","imageLink":"images/one-thousand-and-one-nights.jpg","language":"Arabic","link":"https://en.wikipedia.org/wiki/One_Thousand_and_One_Nights","pages":288,"title":"One Thousand and One Nights","year":1200},{"author":"Unknown","country":"Iceland","imageLink":"images/njals-saga.jpg","language":"Old Norse","link":"https://en.wikipedia.org/wiki/Nj%C3%A1ls_saga","pages":384,"title":"NjĂĄlu0027s Saga","year":1350},{"author":"Jane Austen","country":"United Kingdom","imageLink":"images/pride-and-prejudice.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Pride_and_Prejudice","pages":226,"title":"Pride and Prejudice","year":1813},{"author":"HonorĂ© de Balzac","country":"France","imageLink":"images/le-pere-goriot.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Le_P%C3%A8re_Goriot","pages":443,"title":"Le PĂšre Goriot","year":1835},{"author":"Samuel Beckett","country":"Republic of Ireland","imageLink":"images/molloy-malone-dies-the-unnamable.jpg","language":"French, English","link":"https://en.wikipedia.org/wiki/Molloy_(novel)","pages":256,"title":"Molloy, Malone Dies, The Unnamable, the trilogy","year":1952},{"author":"Giovanni Boccaccio","country":"Italy","imageLink":"images/the-decameron.jpg","language":"Italian","link":"https://en.wikipedia.org/wiki/The_Decameron","pages":1024,"title":"The Decameron","year":1351},{"author":"Jorge Luis Borges","country":"Argentina","imageLink":"images/ficciones.jpg","language":"Spanish","link":"https://en.wikipedia.org/wiki/Ficciones","pages":224,"title":"Ficciones","year":1965},{"author":"Emily BrontĂ«","country":"United Kingdom","imageLink":"images/wuthering-heights.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Wuthering_Heights","pages":342,"title":"Wuthering Heights","year":1847},{"author":"Albert Camus","country":"Algeria, French Empire","imageLink":"images/l-etranger.jpg","language":"French","link":"https://en.wikipedia.org/wiki/The_Stranger_(novel)","pages":185,"title":"The Stranger","year":1942},{"author":"Paul Celan","country":"Romania, France","imageLink":"images/poems-paul-celan.jpg","language":"German","link":"","pages":320,"title":"Poems","year":1952},{"author":"Louis-Ferdinand CĂ©line","country":"France","imageLink":"images/voyage-au-bout-de-la-nuit.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Journey_to_the_End_of_the_Night","pages":505,"title":"Journey to the End of the Night","year":1932},{"author":"Miguel de Cervantes","country":"Spain","imageLink":"images/don-quijote-de-la-mancha.jpg","language":"Spanish","link":"https://en.wikipedia.org/wiki/Don_Quixote","pages":1056,"title":"Don Quijote De La Mancha","year":1610},{"author":"Geoffrey Chaucer","country":"England","imageLink":"images/the-canterbury-tales.jpg","language":"English","link":"https://en.wikipedia.org/wiki/The_Canterbury_Tales","pages":544,"title":"The Canterbury Tales","year":1450},{"author":"Anton Chekhov","country":"Russia","imageLink":"images/stories-of-anton-chekhov.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/List_of_short_stories_by_Anton_Chekhov","pages":194,"title":"Stories","year":1886},{"author":"Joseph Conrad","country":"United Kingdom","imageLink":"images/nostromo.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Nostromo","pages":320,"title":"Nostromo","year":1904},{"author":"Charles Dickens","country":"United Kingdom","imageLink":"images/great-expectations.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Great_Expectations","pages":194,"title":"Great Expectations","year":1861},{"author":"Denis Diderot","country":"France","imageLink":"images/jacques-the-fatalist.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Jacques_the_Fatalist","pages":596,"title":"Jacques the Fatalist","year":1796},{"author":"Alfred Döblin","country":"Germany","imageLink":"images/berlin-alexanderplatz.jpg","language":"German","link":"https://en.wikipedia.org/wiki/Berlin_Alexanderplatz","pages":600,"title":"Berlin Alexanderplatz","year":1929},{"author":"Fyodor Dostoevsky","country":"Russia","imageLink":"images/crime-and-punishment.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/Crime_and_Punishment","pages":551,"title":"Crime and Punishment","year":1866},{"author":"Fyodor Dostoevsky","country":"Russia","imageLink":"images/the-idiot.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/The_Idiot","pages":656,"title":"The Idiot","year":1869},{"author":"Fyodor Dostoevsky","country":"Russia","imageLink":"images/the-possessed.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/Demons_(Dostoyevsky_novel)","pages":768,"title":"The Possessed","year":1872},{"author":"Fyodor Dostoevsky","country":"Russia","imageLink":"images/the-brothers-karamazov.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/The_Brothers_Karamazov","pages":824,"title":"The Brothers Karamazov","year":1880},{"author":"George Eliot","country":"United Kingdom","imageLink":"images/middlemarch.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Middlemarch","pages":800,"title":"Middlemarch","year":1871},{"author":"Ralph Ellison","country":"United States","imageLink":"images/invisible-man.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Invisible_Man","pages":581,"title":"Invisible Man","year":1952},{"author":"Euripides","country":"Greece","imageLink":"images/medea.jpg","language":"Greek","link":"https://en.wikipedia.org/wiki/Medea_(play)","pages":104,"title":"Medea","year":-431},{"author":"William Faulkner","country":"United States","imageLink":"images/absalom-absalom.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Absalom,_Absalom!","pages":313,"title":"Absalom, Absalom!","year":1936},{"author":"William Faulkner","country":"United States","imageLink":"images/the-sound-and-the-fury.jpg","language":"English","link":"https://en.wikipedia.org/wiki/The_Sound_and_the_Fury","pages":326,"title":"The Sound and the Fury","year":1929},{"author":"Gustave Flaubert","country":"France","imageLink":"images/madame-bovary.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Madame_Bovary","pages":528,"title":"Madame Bovary","year":1857},{"author":"Gustave Flaubert","country":"France","imageLink":"images/l-education-sentimentale.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Sentimental_Education","pages":606,"title":"Sentimental Education","year":1869},{"author":"Federico GarcĂa Lorca","country":"Spain","imageLink":"images/gypsy-ballads.jpg","language":"Spanish","link":"https://en.wikipedia.org/wiki/Gypsy_Ballads","pages":218,"title":"Gypsy Ballads","year":1928},{"author":"Gabriel GarcĂa MĂĄrquez","country":"Colombia","imageLink":"images/one-hundred-years-of-solitude.jpg","language":"Spanish","link":"https://en.wikipedia.org/wiki/One_Hundred_Years_of_Solitude","pages":417,"title":"One Hundred Years of Solitude","year":1967},{"author":"Gabriel GarcĂa MĂĄrquez","country":"Colombia","imageLink":"images/love-in-the-time-of-cholera.jpg","language":"Spanish","link":"https://en.wikipedia.org/wiki/Love_in_the_Time_of_Cholera","pages":368,"title":"Love in the Time of Cholera","year":1985},{"author":"Johann Wolfgang von Goethe","country":"Saxe-Weimar","imageLink":"images/faust.jpg","language":"German","link":"https://en.wikipedia.org/wiki/Goethe%27s_Faust","pages":158,"title":"Faust","year":1832},{"author":"Nikolai Gogol","country":"Russia","imageLink":"images/dead-souls.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/Dead_Souls","pages":432,"title":"Dead Souls","year":1842},{"author":"GĂŒnter Grass","country":"Germany","imageLink":"images/the-tin-drum.jpg","language":"German","link":"https://en.wikipedia.org/wiki/The_Tin_Drum","pages":600,"title":"The Tin Drum","year":1959},{"author":"JoĂŁo GuimarĂŁes Rosa","country":"Brazil","imageLink":"images/the-devil-to-pay-in-the-backlands.jpg","language":"Portuguese","link":"https://en.wikipedia.org/wiki/The_Devil_to_Pay_in_the_Backlands","pages":494,"title":"The Devil to Pay in the Backlands","year":1956},{"author":"Knut Hamsun","country":"Norway","imageLink":"images/hunger.jpg","language":"Norwegian","link":"https://en.wikipedia.org/wiki/Hunger_(Hamsun_novel)","pages":176,"title":"Hunger","year":1890},{"author":"Ernest Hemingway","country":"United States","imageLink":"images/the-old-man-and-the-sea.jpg","language":"English","link":"https://en.wikipedia.org/wiki/The_Old_Man_and_the_Sea","pages":128,"title":"The Old Man and the Sea","year":1952},{"author":"Homer","country":"Greece","imageLink":"images/the-iliad-of-homer.jpg","language":"Greek","link":"https://en.wikipedia.org/wiki/Iliad","pages":608,"title":"Iliad","year":-735},{"author":"Homer","country":"Greece","imageLink":"images/the-odyssey-of-homer.jpg","language":"Greek","link":"https://en.wikipedia.org/wiki/Odyssey","pages":374,"title":"Odyssey","year":-800},{"author":"Henrik Ibsen","country":"Norway","imageLink":"images/a-Dolls-house.jpg","language":"Norwegian","link":"https://en.wikipedia.org/wiki/A_Doll%27s_House","pages":68,"title":"A Dollu0027s House","year":1879},{"author":"James Joyce","country":"Irish Free State","imageLink":"images/ulysses.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Ulysses_(novel)","pages":228,"title":"Ulysses","year":1922},{"author":"Franz Kafka","country":"Czechoslovakia","imageLink":"images/stories-of-franz-kafka.jpg","language":"German","link":"https://en.wikipedia.org/wiki/Franz_Kafka_bibliography#Short_stories","pages":488,"title":"Stories","year":1924},{"author":"Franz Kafka","country":"Czechoslovakia","imageLink":"images/the-trial.jpg","language":"German","link":"https://en.wikipedia.org/wiki/The_Trial","pages":160,"title":"The Trial","year":1925},{"author":"Franz Kafka","country":"Czechoslovakia","imageLink":"images/the-castle.jpg","language":"German","link":"https://en.wikipedia.org/wiki/The_Castle_(novel)","pages":352,"title":"The Castle","year":1926},{"author":"KÄlidÄsa","country":"India","imageLink":"images/the-recognition-of-shakuntala.jpg","language":"Sanskrit","link":"https://en.wikipedia.org/wiki/Abhij%C3%B1%C4%81na%C5%9B%C4%81kuntalam","pages":147,"title":"The recognition of Shakuntala","year":150},{"author":"Yasunari Kawabata","country":"Japan","imageLink":"images/the-sound-of-the-mountain.jpg","language":"Japanese","link":"https://en.wikipedia.org/wiki/The_Sound_of_the_Mountain","pages":288,"title":"The Sound of the Mountain","year":1954},{"author":"Nikos Kazantzakis","country":"Greece","imageLink":"images/zorba-the-greek.jpg","language":"Greek","link":"https://en.wikipedia.org/wiki/Zorba_the_Greek","pages":368,"title":"Zorba the Greek","year":1946},{"author":"D. H. Lawrence","country":"United Kingdom","imageLink":"images/sons-and-lovers.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Sons_and_Lovers","pages":432,"title":"Sons and Lovers","year":1913},{"author":"HalldĂłr Laxness","country":"Iceland","imageLink":"images/independent-people.jpg","language":"Icelandic","link":"https://en.wikipedia.org/wiki/Independent_People","pages":470,"title":"Independent People","year":1934},{"author":"Giacomo Leopardi","country":"Italy","imageLink":"images/poems-giacomo-leopardi.jpg","language":"Italian","link":"","pages":184,"title":"Poems","year":1818},{"author":"Doris Lessing","country":"United Kingdom","imageLink":"images/the-golden-notebook.jpg","language":"English","link":"https://en.wikipedia.org/wiki/The_Golden_Notebook","pages":688,"title":"The Golden Notebook","year":1962},{"author":"Astrid Lindgren","country":"Sweden","imageLink":"images/pippi-longstocking.jpg","language":"Swedish","link":"https://en.wikipedia.org/wiki/Pippi_Longstocking","pages":160,"title":"Pippi Longstocking","year":1945},{"author":"Lu Xun","country":"China","imageLink":"images/diary-of-a-madman.jpg","language":"Chinese","link":"https://en.wikipedia.org/wiki/A_Madman%27s_Diary","pages":389,"title":"Diary of a Madman","year":1918},{"author":"Naguib Mahfouz","country":"Egypt","imageLink":"images/children-of-gebelawi.jpg","language":"Arabic","link":"https://en.wikipedia.org/wiki/Children_of_Gebelawi","pages":355,"title":"Children of Gebelawi","year":1959},{"author":"Thomas Mann","country":"Germany","imageLink":"images/buddenbrooks.jpg","language":"German","link":"https://en.wikipedia.org/wiki/Buddenbrooks","pages":736,"title":"Buddenbrooks","year":1901},{"author":"Thomas Mann","country":"Germany","imageLink":"images/the-magic-mountain.jpg","language":"German","link":"https://en.wikipedia.org/wiki/The_Magic_Mountain","pages":720,"title":"The Magic Mountain","year":1924},{"author":"Herman Melville","country":"United States","imageLink":"images/moby-dick.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Moby-Dick","pages":378,"title":"Moby Dick","year":1851},{"author":"Michel de Montaigne","country":"France","imageLink":"images/essais.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Essays_(Montaigne)","pages":404,"title":"Essays","year":1595},{"author":"Elsa Morante","country":"Italy","imageLink":"images/history.jpg","language":"Italian","link":"https://en.wikipedia.org/wiki/History_(novel)","pages":600,"title":"History","year":1974},{"author":"Toni Morrison","country":"United States","imageLink":"images/beloved.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Beloved_(novel)","pages":321,"title":"Beloved","year":1987},{"author":"Murasaki Shikibu","country":"Japan","imageLink":"images/the-tale-of-genji.jpg","language":"Japanese","link":"https://en.wikipedia.org/wiki/The_Tale_of_Genji","pages":1360,"title":"The Tale of Genji","year":1006},{"author":"Robert Musil","country":"Austria","imageLink":"images/the-man-without-qualities.jpg","language":"German","link":"https://en.wikipedia.org/wiki/The_Man_Without_Qualities","pages":365,"title":"The Man Without Qualities","year":1931},{"author":"Vladimir Nabokov","country":"Russia/United States","imageLink":"images/lolita.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Lolita","pages":317,"title":"Lolita","year":1955},{"author":"George Orwell","country":"United Kingdom","imageLink":"images/nineteen-eighty-four.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Nineteen_Eighty-Four","pages":272,"title":"Nineteen Eighty-Four","year":1949},{"author":"Ovid","country":"Roman Empire","imageLink":"images/the-metamorphoses-of-ovid.jpg","language":"Classical Latin","link":"https://en.wikipedia.org/wiki/Metamorphoses","pages":576,"title":"Metamorphoses","year":100},{"author":"Fernando Pessoa","country":"Portugal","imageLink":"images/the-book-of-disquiet.jpg","language":"Portuguese","link":"https://en.wikipedia.org/wiki/The_Book_of_Disquiet","pages":272,"title":"The Book of Disquiet","year":1928},{"author":"Edgar Allan Poe","country":"United States","imageLink":"images/tales-and-poems-of-edgar-allan-poe.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Edgar_Allan_Poe_bibliography#Tales","pages":842,"title":"Tales","year":1950},{"author":"Marcel Proust","country":"France","imageLink":"images/a-la-recherche-du-temps-perdu.jpg","language":"French","link":"https://en.wikipedia.org/wiki/In_Search_of_Lost_Time","pages":2408,"title":"In Search of Lost Time","year":1920},{"author":"François Rabelais","country":"France","imageLink":"images/gargantua-and-pantagruel.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Gargantua_and_Pantagruel","pages":623,"title":"Gargantua and Pantagruel","year":1533},{"author":"Juan Rulfo","country":"Mexico","imageLink":"images/pedro-paramo.jpg","language":"Spanish","link":"https://en.wikipedia.org/wiki/Pedro_P%C3%A1ramo","pages":124,"title":"Pedro PĂĄramo","year":1955},{"author":"Rumi","country":"Sultanate of Rum","imageLink":"images/the-masnavi.jpg","language":"Persian","link":"https://en.wikipedia.org/wiki/Masnavi","pages":438,"title":"The Masnavi","year":1236},{"author":"Salman Rushdie","country":"United Kingdom, India","imageLink":"images/midnights-children.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Midnight%27s_Children","pages":536,"title":"Midnightu0027s Children","year":1981},{"author":"Saadi","country":"Persia, Persian Empire","imageLink":"images/bostan.jpg","language":"Persian","link":"https://en.wikipedia.org/wiki/Bustan_(book)","pages":298,"title":"Bostan","year":1257},{"author":"Tayeb Salih","country":"Sudan","imageLink":"images/season-of-migration-to-the-north.jpg","language":"Arabic","link":"https://en.wikipedia.org/wiki/Season_of_Migration_to_the_North","pages":139,"title":"Season of Migration to the North","year":1966},{"author":"JosĂ© Saramago","country":"Portugal","imageLink":"images/blindness.jpg","language":"Portuguese","link":"https://en.wikipedia.org/wiki/Blindness_(novel)","pages":352,"title":"Blindness","year":1995},{"author":"William Shakespeare","country":"England","imageLink":"images/hamlet.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Hamlet","pages":432,"title":"Hamlet","year":1603},{"author":"William Shakespeare","country":"England","imageLink":"images/king-lear.jpg","language":"English","link":"https://en.wikipedia.org/wiki/King_Lear","pages":384,"title":"King Lear","year":1608},{"author":"William Shakespeare","country":"England","imageLink":"images/othello.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Othello","pages":314,"title":"Othello","year":1609},{"author":"Sophocles","country":"Greece","imageLink":"images/oedipus-the-king.jpg","language":"Greek","link":"https://en.wikipedia.org/wiki/Oedipus_the_King","pages":88,"title":"Oedipus the King","year":-430},{"author":"Stendhal","country":"France","imageLink":"images/le-rouge-et-le-noir.jpg","language":"French","link":"https://en.wikipedia.org/wiki/The_Red_and_the_Black","pages":576,"title":"The Red and the Black","year":1830},{"author":"Laurence Sterne","country":"England","imageLink":"images/the-life-and-opinions-of-tristram-shandy.jpg","language":"English","link":"https://en.wikipedia.org/wiki/The_Life_and_Opinions_of_Tristram_Shandy,_Gentleman","pages":640,"title":"The Life And Opinions of Tristram Shandy","year":1760},{"author":"Italo Svevo","country":"Italy","imageLink":"images/confessions-of-zeno.jpg","language":"Italian","link":"https://en.wikipedia.org/wiki/Zeno%27s_Conscience","pages":412,"title":"Confessions of Zeno","year":1923},{"author":"Jonathan Swift","country":"Ireland","imageLink":"images/gullivers-travels.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Gulliver%27s_Travels","pages":178,"title":"Gulliveru0027s Travels","year":1726},{"author":"Leo Tolstoy","country":"Russia","imageLink":"images/war-and-peace.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/War_and_Peace","pages":1296,"title":"War and Peace","year":1867},{"author":"Leo Tolstoy","country":"Russia","imageLink":"images/anna-karenina.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/Anna_Karenina","pages":864,"title":"Anna Karenina","year":1877},{"author":"Leo Tolstoy","country":"Russia","imageLink":"images/the-death-of-ivan-ilyich.jpg","language":"Russian","link":"https://en.wikipedia.org/wiki/The_Death_of_Ivan_Ilyich","pages":92,"title":"The Death of Ivan Ilyich","year":1886},{"author":"Mark Twain","country":"United States","imageLink":"images/the-adventures-of-huckleberry-finn.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Adventures_of_Huckleberry_Finn","pages":224,"title":"The Adventures of Huckleberry Finn","year":1884},{"author":"Valmiki","country":"India","imageLink":"images/ramayana.jpg","language":"Sanskrit","link":"https://en.wikipedia.org/wiki/Ramayana","pages":152,"title":"Ramayana","year":-450},{"author":"Virgil","country":"Roman Empire","imageLink":"images/the-aeneid.jpg","language":"Classical Latin","link":"https://en.wikipedia.org/wiki/Aeneid","pages":442,"title":"The Aeneid","year":-23},{"author":"Vyasa","country":"India","imageLink":"images/the-mahab-harata.jpg","language":"Sanskrit","link":"https://en.wikipedia.org/wiki/Mahabharata","pages":276,"title":"Mahabharata","year":-700},{"author":"Walt Whitman","country":"United States","imageLink":"images/leaves-of-grass.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Leaves_of_Grass","pages":152,"title":"Leaves of Grass","year":1855},{"author":"Virginia Woolf","country":"United Kingdom","imageLink":"images/mrs-dalloway.jpg","language":"English","link":"https://en.wikipedia.org/wiki/Mrs_Dalloway","pages":216,"title":"Mrs Dalloway","year":1925},{"author":"Virginia Woolf","country":"United Kingdom","imageLink":"images/to-the-lighthouse.jpg","language":"English","link":"https://en.wikipedia.org/wiki/To_the_Lighthouse","pages":209,"title":"To the Lighthouse","year":1927},{"author":"Marguerite Yourcenar","country":"France/Belgium","imageLink":"images/memoirs-of-hadrian.jpg","language":"French","link":"https://en.wikipedia.org/wiki/Memoirs_of_Hadrian","pages":408,"title":"Memoirs of Hadrian","year":1951}]';
We need to parse this data as JSON so JavaScript can process it.
my_big_json = JSON.parse(my_big_json);
for (var i = 0; i < my_big_json.length; i++) {
console.log(i + 1, " -> ", my_big_json[i]);
}
To ensure that the loading process was successful, Iâm iterating over the JSON dataset and printing each entry. You should see the following in your console log.
Building Search Index
Now we will build the search index in a variable called idx using the lunr() function. This step requires 3 things:
- Lunr returns a document reference for every document that matches a search query. And we need to tell Lunr which field in our dataset should be the reference. Usually, this reference is a numeric ID unique to every document. Since our dataset does not contain such a field Iâll use the
linkfield as the reference field. - Lunr also requires a list of fields that should be part of the search index. For this example, I want to search on
author,title, andcountry. - Lastly, Lunr requires our dataset⊠the
my_big_jsonvariable.
We can now call the lunr() function to build our search index idx.
var idx = lunr(function () {
this.ref('link')
this.field('author')
this.field('title')
this.field('country')
my_big_json.forEach(function (doc) {
this.add(doc)
}, this)
});
If there were no errors in your browserâs console log then our index built was successful. Letâs take it for a test drive.
Looking for Books in Our Dataset With Lunr
Letâs first see if there are any documents containing the word adventures:
results = idx.search("adventures");
console.log('Results: ', results.length);
We should see the following in our console log:
Results: 1
Alright. So there is 1 document that matches the search query adventures. But how do we display it?
As I mentioned before, Lunr returns the reference of the matching document. But not the document itself. Meaning if we print results weâll see the following.
Here results contains an array of objects with a single element. And that elementâs ref field contains a value. This is because we used the link field as the reference. To show the full document, weâll need to work a bit harder.
results = idx.search("adventures");
console.log('Results: ', results.length);
var results_full = results.map(function (item) {
return my_big_json.filter(function (value, index, arr) {
return value.link == item.ref;
})[0];
});
console.log(results_full);
In the above code, weâre iterating through the results using the map() function. We then find documents in my_big_json for all the references in the result set. So results_full contains the complete search results.
0: Object { author: "Mark Twain", country: "United States", imageLink: "images/the-adventures-of-huckleberry-finn.jpg", ⊠}
Letâs repeat the search for the keyword india. The code is as follows.
results = idx.search("india");
console.log('Results: ', results.length);
var results_full = results.map(function (item) {
return my_big_json.filter(function (value, index, arr) {
return value.link == item.ref;
})[0];
});
console.log(results_full);
And the results are:
Results: 4
0: Object { author: "KÄlidÄsa", country: "India", imageLink: "images/the-recognition-of-shakuntala.jpg", ⊠}
1: Object { author: "Valmiki", country: "India", imageLink: "images/ramayana.jpg", ⊠}
2: Object { author: "Vyasa", country: "India", imageLink: "images/the-mahab-harata.jpg", ⊠}
3: Object { author: "Salman Rushdie", country: "United Kingdom, India", imageLink: "images/midnights-children.jpg", ⊠}
And itâs that simple! Adding search for any array of JSON objects only requires 5 easy steps:
- Call
Lunr.js. - Identify the reference fields and the search fields.
- Build the search index by iterating over the dataset.
- Call the
search()method to search the index and return the matching references. - And finally, retrieve the documents for the matching references.
Prebuilding Lunr.jsâs Search Index
You may have noticed that the search index takes some time to build on every page refresh. The time may be imperceptible right now. But it wonât be when lunr.html is on a remote server. Lunr allows pre-building the search index to make the search more responsive.
There are 2 ways of pre-building the index. The first method is to serialize the index after building it. Since weâve already created the index in our tutorial weâll use this method.
var serializedIdx = JSON.stringify(idx);
console.log(serializedIdx);
We would then replace my_big_json with the serialized string. Our index load command would also change.
var my_big_json = lunr.Index.load(JSON.parse(serializedIdx));
The second method involves calling the above commands in CLI. This method is great for running in a CI/CD pipeline. Iâll talk about this method more later on.
Lunr.js Search Tips and Tricks
Web search engines like DuckDuckGo provide a way to prioritize search terms. For example, a + sign will include a search term and - will exclude it.
Lunr provides similar features to prioritize search terms or search fields. + will include a search term and - will exclude it. The ~ symbol allows fuzzy matching. The ^ symbol allows weighting search terms. And the : symbol allows search for specific fields.
For example, to find the best books published in England but not by Shakespeare, our Lunr query will be:
results = idx.search("country:England -author:Shakespeare");
This gives me 2 results:
0: {author: 'Geoffrey Chaucer', country: 'England', imageLink: 'images/the-canterbury-tales.jpg', language: 'English', link: 'https://en.wikipedia.org/wiki/The_Canterbury_Tales', âŠ}
1: {author: 'Laurence Sterne', country: 'England', imageLink: 'images/the-life-and-opinions-of-tristram-shandy.jpg', language: 'English', link: 'https://en.wikipedia.org/wiki/The_Life_and_Opinions_of_Tristram_Shandy,_Gentleman', âŠ}
Lunr in Action: findmymastodon.com!
findmymastodon.com helps users find, well, Mastodon instances. These instances often cater to specific languages, themes, and interests. And so the website needed a search engine.
I started by first building the dataset using Python. The dataset contains metadata for thousands of Mastodon instances currently live. I then used Node to create a serialized Lunr index from the original JSON. This Lunr index is then loaded as a static asset. Search executes against this index and the Mastodon instances, if found, displayed on the search page. You can browse the JavaScript source code here.
Conclusion
Lunr can prove to be a useful ally in web-dev. Itâs especially great for static websites which donât rely on an active backend. Support for pre-built indices using CLI is a huge performance bonus. This allows using CI/CD to fetch data from a remote backend and create the index. Meaning the backend no longer needs to remain active to serve search requests.
Client-side search is a new thing for me. Iâve been a DevOps/cloud guy for a long time and Iâm eager to find out how this can improve security and optimize costs. Web browsers are becoming more sophisticated every day. Letting them handle the heavy-lifting for search might grant performance improvements, improved user experiences, and lower cloud costs.
Thanks for reading this how-to, and I hope it sparked some creative ideas in your head. Happy coding đ
Credit: Source link