{"id":3044,"date":"2020-09-02T08:51:00","date_gmt":"2020-09-02T08:51:00","guid":{"rendered":"http:\/\/the-codest.localhost\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/"},"modified":"2026-04-24T11:34:04","modified_gmt":"2026-04-24T11:34:04","slug":"asynchroniczny-i-jednowatkowy-javascript-w-petli-zdarzen","status":"publish","type":"post","link":"https:\/\/thecodest.co\/pl\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/","title":{"rendered":"Asynchroniczny i jednow\u0105tkowy JavaScript?"},"content":{"rendered":"<ul class=\"wp-block-list\">\n<li><strong>Czas dzia\u0142ania<\/strong><\/li>\n<\/ul>\n\n\n\n<p><a href=\"https:\/\/thecodest.co\/pl\/blog\/hire-javascript-developer\/\">JavaScript<\/a> jest j\u0119zykiem interpretowanym, a nie kompilowanym. Oznacza to, \u017ce potrzebuje on interpretera, kt\u00f3ry konwertuje plik <a href=\"https:\/\/thecodest.co\/pl\/blog\/hire-vue-js-developers\/\">JS<\/a> <a href=\"https:\/\/thecodest.co\/pl\/dictionary\/what-is-code-refactoring\/\">kod<\/a> do kodu maszynowego. Istnieje kilka rodzaj\u00f3w interpreter\u00f3w (zwanych silnikami). Najpopularniejsze silniki przegl\u0105darek to V8 (Chrome), Quantum (Firefox) i WebKit (Safari). Nawiasem m\u00f3wi\u0105c, V8 jest r\u00f3wnie\u017c u\u017cywany w popularnym \u015brodowisku uruchomieniowym innym ni\u017c przegl\u0105darka, <a href=\"https:\/\/thecodest.co\/pl\/blog\/find-your-node-js-expert-for-hire-today\/\">Node.js<\/a>.<\/p>\n\n\n\n<p>Ka\u017cdy silnik zawiera stert\u0119 pami\u0119ci, stos wywo\u0142a\u0144, p\u0119tl\u0119 zdarze\u0144, kolejk\u0119 wywo\u0142a\u0144 zwrotnych i interfejs WebAPI z \u017c\u0105daniami HTTP, licznikami czasu, zdarzeniami itp., wszystkie zaimplementowane na sw\u00f3j w\u0142asny spos\u00f3b w celu szybszej i bezpieczniejszej interpretacji kodu JS.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"\/app\/uploads\/2024\/05\/runtime-architecture.png\" alt=\"Rozw\u00f3j JavaScript\" title=\"Rozw\u00f3j JavaScript\"\/><\/figure>\n\n\n\n<p><em>Podstawowa architektura \u015brodowiska uruchomieniowego JS. Autor: Alex Zlatkov<\/em><\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Pojedynczy w\u0105tek<\/strong><\/h2>\n\n\n\n<p>J\u0119zyk jednow\u0105tkowy to j\u0119zyk z pojedynczym stosem wywo\u0142a\u0144 i pojedyncz\u0105 stert\u0105 pami\u0119ci. Oznacza to, \u017ce w danym momencie wykonywana jest tylko jedna operacja.<\/p>\n\n\n\n<p>A&nbsp;<code>stos<\/code>&nbsp;jest ci\u0105g\u0142ym regionem pami\u0119ci, alokuj\u0105cym lokalny kontekst dla ka\u017cdej wykonywanej funkcji.<\/p>\n\n\n\n<p>A&nbsp;<code>sterta<\/code>&nbsp;to znacznie wi\u0119kszy region, przechowuj\u0105cy wszystko, co zosta\u0142o przydzielone dynamicznie.<\/p>\n\n\n\n<p>A&nbsp;<code>stos wywo\u0142a\u0144<\/code>&nbsp;jest <a href=\"https:\/\/thecodest.co\/pl\/blog\/app-data-collection-security-risks-value-and-types-explored\/\">dane<\/a> kt\u00f3ra zasadniczo rejestruje, gdzie jeste\u015bmy w programie.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Stos wywo\u0142a\u0144<\/strong><\/h3>\n\n\n\n<p>Napiszmy prosty kod i prze\u015bled\u017amy, co dzieje si\u0119 na stosie wywo\u0142a\u0144.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"\/app\/uploads\/2024\/05\/stack.gif\" alt=\"Rozw\u00f3j oprogramowania JavaScript\" title=\"Rozw\u00f3j oprogramowania JavaScript\"\/><\/figure>\n\n\n\n<p>Jak wida\u0107, funkcje s\u0105 dodawane do stosu, wykonywane, a nast\u0119pnie usuwane. Jest to tak zwany spos\u00f3b LIFO - Last In, First Out. Ka\u017cdy wpis na stosie wywo\u0142a\u0144 jest nazywany&nbsp;<code>ramka stosu<\/code>.<\/p>\n\n\n\n<p>Znajomo\u015b\u0107 stosu wywo\u0142a\u0144 jest przydatna do odczytywania \u015blad\u00f3w stosu b\u0142\u0119d\u00f3w. Og\u00f3lnie rzecz bior\u0105c, dok\u0142adna przyczyna b\u0142\u0119du znajduje si\u0119 na g\u00f3rze w pierwszej linii, chocia\u017c kolejno\u015b\u0107 wykonywania kodu jest oddolna.<\/p>\n\n\n\n<p>Czasami mo\u017cna poradzi\u0107 sobie z popularnym b\u0142\u0119dem, zg\u0142aszanym przez\u00a0<code>Przekroczono maksymalny rozmiar stosu wywo\u0142a\u0144<\/code>. Mo\u017cna to \u0142atwo uzyska\u0107 za pomoc\u0105 rekurencji:<\/p>\n\n\n\n<pre class=\"wp-block-code\"><code lang=\"javascript\" class=\"language-javascript\">function foo() {\n    foo()\n}\nfoo()<\/code><\/pre>\n\n\n\n<p>i nasza przegl\u0105darka lub terminal zawiesza si\u0119. Ka\u017cda przegl\u0105darka, nawet w r\u00f3\u017cnych wersjach, ma inny limit wielko\u015bci stosu wywo\u0142a\u0144. W zdecydowanej wi\u0119kszo\u015bci przypadk\u00f3w s\u0105 one wystarczaj\u0105ce i problemu nale\u017cy szuka\u0107 gdzie indziej.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Zablokowany stos wywo\u0142a\u0144<\/strong><\/h3>\n\n\n\n<p>Oto przyk\u0142ad blokowania w\u0105tku JS. Spr\u00f3bujmy odczyta\u0107 plik&nbsp;<code>foo<\/code>&nbsp;i plik&nbsp;<code>pasek<\/code>&nbsp;przy u\u017cyciu <a href=\"https:\/\/thecodest.co\/pl\/dictionary\/what-is-node-js-used-for\/\">W\u0119ze\u0142<\/a>Funkcja synchroniczna .js&nbsp;<code>readFileSync<\/code>.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"\/app\/uploads\/2024\/05\/blocking.gif\" alt=\"Kod JavaScript\" title=\"Kod JavaScript\"\/><\/figure>\n\n\n\n<p>To jest zap\u0119tlony GIF. Jak wida\u0107, silnik JS czeka do pierwszego wywo\u0142ania w pliku&nbsp;<code>readFileSync<\/code>&nbsp;jest zako\u0144czona. Ale tak si\u0119 nie stanie, poniewa\u017c nie ma&nbsp;<code>foo<\/code>&nbsp;wi\u0119c druga funkcja nigdy nie zostanie wywo\u0142ana.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Zachowanie asynchroniczne<\/strong><\/h2>\n\n\n\n<p>Jednak JS mo\u017ce by\u0107 r\u00f3wnie\u017c nieblokuj\u0105cy i zachowywa\u0107 si\u0119 tak, jakby by\u0142 wielow\u0105tkowy. Oznacza to, \u017ce nie czeka on na odpowied\u017a z polecenia <a href=\"https:\/\/thecodest.co\/pl\/blog\/compare-staff-augmentation-firms-that-excel-in-api-team-staffing-for-financial-technology-projects\/\">API<\/a> i mo\u017ce kontynuowa\u0107 wykonywanie kodu. Jest to mo\u017cliwe dzi\u0119ki silnikom JS, kt\u00f3re u\u017cywaj\u0105 (pod mask\u0105) prawdziwych j\u0119zyk\u00f3w wielow\u0105tkowych, takich jak C++ (Chrome) lub Rust (Firefox). Zapewniaj\u0105 one <a href=\"https:\/\/thecodest.co\/pl\/blog\/why-us-companies-are-opting-for-polish-developers\/\">my<\/a> z <a href=\"https:\/\/thecodest.co\/pl\/blog\/find-your-ideal-stack-for-web-development\/\">Sie\u0107<\/a> API pod mask\u0105 przegl\u0105darki lub np. I\/O API pod Node.js.<\/p>\n\n\n\n<figure class=\"wp-block-image\"><img decoding=\"async\" src=\"\/app\/uploads\/2024\/05\/callback-queue.gif\" alt=\"J\u0119zyk programowania JavaScript\" title=\"J\u0119zyk programowania JavaScript\"\/><\/figure>\n\n\n\n<p>Na powy\u017cszym GIF-ie widzimy, \u017ce pierwsza funkcja jest wypychana na stos wywo\u0142a\u0144 i&nbsp;<code>Cze\u015b\u0107<\/code>&nbsp;jest natychmiast wykonywana w konsoli.<\/p>\n\n\n\n<p>Nast\u0119pnie wywo\u0142ujemy&nbsp;<code>setTimeout<\/code>&nbsp;dostarczana przez WebAPI przegl\u0105darki. Przechodzi ona do stosu wywo\u0142a\u0144 i jej asynchronicznego wywo\u0142ania zwrotnego&nbsp;<code>foo<\/code>&nbsp;funkcja przechodzi do kolejki WebApi, gdzie czeka na po\u0142\u0105czenie, kt\u00f3re ma nast\u0105pi\u0107 po 3 sekundach.<\/p>\n\n\n\n<p>W mi\u0119dzyczasie program kontynuuje kod i widzimy&nbsp;<code>Cze\u015b\u0107, nie jestem zablokowany<\/code>&nbsp;w konsoli.<\/p>\n\n\n\n<p>Po wywo\u0142aniu, ka\u017cda funkcja w kolejce WebAPI trafia do pliku&nbsp;<code>Kolejka wywo\u0142ania zwrotnego<\/code>. Jest to miejsce, w kt\u00f3rym funkcje czekaj\u0105, a\u017c stos wywo\u0142a\u0144 b\u0119dzie pusty. Gdy tak si\u0119 stanie, s\u0105 tam przenoszone jedna po drugiej.<\/p>\n\n\n\n<p>Tak wi\u0119c, kiedy nasz&nbsp;<code>setTimeout<\/code>&nbsp;timer zako\u0144czy odliczanie, nasz&nbsp;<code>foo<\/code>&nbsp;funkcja przechodzi do kolejki wywo\u0142ania zwrotnego, czeka, a\u017c stos wywo\u0142a\u0144 stanie si\u0119 dost\u0119pny, przechodzi tam, jest wykonywana i widzimy&nbsp;<code>Cze\u015b\u0107 z asynchronicznego wywo\u0142ania zwrotnego<\/code>&nbsp;w konsoli.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>P\u0119tla zdarze\u0144<\/strong><\/h3>\n\n\n\n<p>Pytanie brzmi, sk\u0105d \u015brodowisko wykonawcze wie, \u017ce stos wywo\u0142a\u0144 jest pusty i jak wywo\u0142ywane jest zdarzenie w kolejce wywo\u0142a\u0144 zwrotnych? Poznaj p\u0119tl\u0119 zdarze\u0144. Jest ona cz\u0119\u015bci\u0105 silnika JS. Proces ten stale sprawdza, czy stos wywo\u0142a\u0144 jest pusty, a je\u015bli tak, monitoruje, czy w kolejce wywo\u0142a\u0144 zwrotnych znajduje si\u0119 zdarzenie oczekuj\u0105ce na wywo\u0142anie.<\/p>\n\n\n\n<p>To ca\u0142a magia za kulisami!<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Podsumowuj\u0105c teori\u0119<\/strong><\/h2>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Wsp\u00f3\u0142bie\u017cno\u015b\u0107 i r\u00f3wnoleg\u0142o\u015b\u0107<\/strong><\/h3>\n\n\n\n<p><code>Wsp\u00f3\u0142bie\u017cno\u015b\u0107<\/code>&nbsp;oznacza wykonywanie wielu zada\u0144 w tym samym czasie, ale nie jednocze\u015bnie. Np. dwa zadania dzia\u0142aj\u0105 w nak\u0142adaj\u0105cych si\u0119 okresach czasu.<\/p>\n\n\n\n<p><code>R\u00f3wnoleg\u0142o\u015b\u0107<\/code>&nbsp;oznacza wykonywanie dw\u00f3ch lub wi\u0119cej zada\u0144 jednocze\u015bnie, np. wykonywanie wielu oblicze\u0144 w tym samym czasie.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>W\u0105tki i procesy<\/strong><\/h3>\n\n\n\n<p><code>Nici<\/code>&nbsp;s\u0105 sekwencj\u0105 wykonywania kodu, kt\u00f3re mog\u0105 by\u0107 wykonywane niezale\u017cnie od siebie.<\/p>\n\n\n\n<p><code>Proces<\/code>&nbsp;jest instancj\u0105 uruchomionego programu. Program mo\u017ce mie\u0107 wiele proces\u00f3w.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Synchroniczne i asynchroniczne<\/strong><\/h3>\n\n\n\n<p>W&nbsp;<code>synchroniczny<\/code>&nbsp;W programowaniu zadania s\u0105 wykonywane jedno po drugim. Ka\u017cde zadanie czeka na zako\u0144czenie poprzedniego i dopiero wtedy jest wykonywane.<\/p>\n\n\n\n<p>W&nbsp;<code>asynchroniczny<\/code>&nbsp;programowanie, gdy jedno zadanie jest wykonywane, mo\u017cna prze\u0142\u0105czy\u0107 si\u0119 na inne zadanie bez czekania na zako\u0144czenie poprzedniego.<\/p>\n\n\n\n<h3 class=\"wp-block-heading\"><strong>Synchroniczne i asynchroniczne w \u015brodowisku jedno- i wielow\u0105tkowym<\/strong><\/h3>\n\n\n\n<p><code>Synchroniczne z pojedynczym w\u0105tkiem<\/code>: Zadania s\u0105 wykonywane jedno po drugim. Ka\u017cde zadanie czeka na wykonanie poprzedniego zadania.<\/p>\n\n\n\n<p><code>Synchroniczny z wieloma w\u0105tkami<\/code>: Zadania s\u0105 wykonywane w r\u00f3\u017cnych w\u0105tkach, ale czekaj\u0105 na inne zadania wykonywane w innym w\u0105tku.<\/p>\n\n\n\n<p><code>Asynchroniczny z pojedynczym w\u0105tkiem<\/code>: Zadania zaczynaj\u0105 by\u0107 wykonywane bez oczekiwania na zako\u0144czenie innego zadania. W danym momencie mo\u017ce by\u0107 wykonywane tylko jedno zadanie.<\/p>\n\n\n\n<p><code>Asynchroniczny z wieloma w\u0105tkami<\/code>: Zadania s\u0105 wykonywane w r\u00f3\u017cnych w\u0105tkach bez oczekiwania na zako\u0144czenie innych zada\u0144 i ko\u0144cz\u0105 swoje wykonywanie niezale\u017cnie.<\/p>\n\n\n\n<h2 class=\"wp-block-heading\"><strong>Klasyfikacja JavaScript<\/strong><\/h2>\n\n\n\n<p>Je\u015bli we\u017amiemy pod uwag\u0119, jak silniki JS dzia\u0142aj\u0105 pod mask\u0105, mo\u017cemy sklasyfikowa\u0107 JS jako asynchroniczny i jednow\u0105tkowy j\u0119zyk interpretowany. S\u0142owo \"interpretowany\" jest bardzo wa\u017cne, poniewa\u017c oznacza, \u017ce j\u0119zyk zawsze b\u0119dzie zale\u017cny od czasu wykonywania i nigdy nie b\u0119dzie tak szybki jak j\u0119zyki kompilowane z wbudowan\u0105 wielow\u0105tkowo\u015bci\u0105.<\/p>\n\n\n\n<p>Warto zauwa\u017cy\u0107, \u017ce Node.js mo\u017ce osi\u0105gn\u0105\u0107 prawdziw\u0105 wielow\u0105tkowo\u015b\u0107, pod warunkiem, \u017ce ka\u017cdy w\u0105tek jest uruchamiany jako oddzielny proces. Istniej\u0105 do tego biblioteki, ale Node.js ma wbudowan\u0105 funkcj\u0119 o nazwie&nbsp;<a href=\"https:\/\/nodejs.org\/api\/worker_threads.html#worker_threads_worker_threads\">W\u0105tki pracownicze<\/a>.<\/p>\n\n\n\n<p>Wszystkie GIF-y p\u0119tli zdarze\u0144 pochodz\u0105 z&nbsp;<a href=\"https:\/\/github.com\/latentflip\/loupe\">Lupa<\/a>&nbsp;stworzona przez Philipa Robertsa, w kt\u00f3rej mo\u017cna testowa\u0107 asynchroniczne scenariusze.<\/p>\n\n\n\n<p><b>Czytaj wi\u0119cej:<\/b><\/p>\n\n\n\n<p><a href=\"https:\/\/thecodest.co\/blog\/why-you-should-probably-use-typescript\">Dlaczego (prawdopodobnie) powiniene\u015b u\u017cywa\u0107 Typescript?<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/thecodest.co\/blog\/quality-first-5-easy-steps-to-lint-your-code-with-github-workflows-in-javascript-project\/\">Jako\u015b\u0107 przede wszystkim! 5 prostych krok\u00f3w do lintowania kodu za pomoc\u0105 przep\u0142yw\u00f3w pracy GitHub w projekcie JavaScript<\/a><\/p>\n\n\n\n<p><a href=\"https:\/\/thecodest.co\/blog\/how-to-improve-vue-js-apps-some-practical-tips\/\">Jak ulepszy\u0107 aplikacje Vue.js? Kilka praktycznych wskaz\u00f3wek<\/a><\/p>","protected":false},"excerpt":{"rendered":"<p>JavaScript jest j\u0119zykiem jednow\u0105tkowym, a jednocze\u015bnie nieblokuj\u0105cym, asynchronicznym i wsp\u00f3\u0142bie\u017cnym. Ten artyku\u0142 wyja\u015bni ci, jak to si\u0119 dzieje.<\/p>","protected":false},"author":2,"featured_media":3045,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"inline_featured_image":false,"footnotes":""},"categories":[8],"tags":[],"class_list":["post-3044","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-software-development"],"acf":[],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v27.3 (Yoast SEO v27.3) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>Asynchronous and Single-threaded JavaScript? - The Codest<\/title>\n<meta name=\"description\" content=\"JavaScript is a single-threaded language and, at the same time, also non-blocking, asynchronous and concurrent. This article will explain to you how it happens.\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/thecodest.co\/pl\/blog\/asynchroniczny-i-jednowatkowy-javascript-w-petli-zdarzen\/\" \/>\n<meta property=\"og:locale\" content=\"pl_PL\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Asynchronous and Single-threaded JavaScript?\" \/>\n<meta property=\"og:description\" content=\"JavaScript is a single-threaded language and, at the same time, also non-blocking, asynchronous and concurrent. This article will explain to you how it happens.\" \/>\n<meta property=\"og:url\" content=\"https:\/\/thecodest.co\/pl\/blog\/asynchroniczny-i-jednowatkowy-javascript-w-petli-zdarzen\/\" \/>\n<meta property=\"og:site_name\" content=\"The Codest\" \/>\n<meta property=\"article:published_time\" content=\"2020-09-02T08:51:00+00:00\" \/>\n<meta property=\"article:modified_time\" content=\"2026-04-24T11:34:04+00:00\" \/>\n<meta property=\"og:image\" content=\"https:\/\/thecodest.co\/app\/uploads\/2024\/05\/cover-image-16.jpg\" \/>\n\t<meta property=\"og:image:width\" content=\"1920\" \/>\n\t<meta property=\"og:image:height\" content=\"1080\" \/>\n\t<meta property=\"og:image:type\" content=\"image\/jpeg\" \/>\n<meta name=\"author\" content=\"thecodest\" \/>\n<meta name=\"twitter:card\" content=\"summary_large_image\" \/>\n<meta name=\"twitter:label1\" content=\"Written by\" \/>\n\t<meta name=\"twitter:data1\" content=\"thecodest\" \/>\n\t<meta name=\"twitter:label2\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data2\" content=\"6 minut\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\\\/\\\/schema.org\",\"@graph\":[{\"@type\":\"Article\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#article\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/\"},\"author\":{\"name\":\"thecodest\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/#\\\/schema\\\/person\\\/7e3fe41dfa4f4e41a7baad4c6e0d4f76\"},\"headline\":\"Asynchronous and Single-threaded JavaScript?\",\"datePublished\":\"2020-09-02T08:51:00+00:00\",\"dateModified\":\"2026-04-24T11:34:04+00:00\",\"mainEntityOfPage\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/\"},\"wordCount\":1058,\"commentCount\":0,\"publisher\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/#organization\"},\"image\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/thecodest.co\\\/app\\\/uploads\\\/2024\\\/05\\\/cover-image-16.jpg\",\"articleSection\":[\"Software Development\"],\"inLanguage\":\"pl-PL\",\"potentialAction\":[{\"@type\":\"CommentAction\",\"name\":\"Comment\",\"target\":[\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#respond\"]}]},{\"@type\":\"WebPage\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/\",\"url\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/\",\"name\":\"Asynchronous and Single-threaded JavaScript? - The Codest\",\"isPartOf\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/#website\"},\"primaryImageOfPage\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#primaryimage\"},\"image\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#primaryimage\"},\"thumbnailUrl\":\"https:\\\/\\\/thecodest.co\\\/app\\\/uploads\\\/2024\\\/05\\\/cover-image-16.jpg\",\"datePublished\":\"2020-09-02T08:51:00+00:00\",\"dateModified\":\"2026-04-24T11:34:04+00:00\",\"description\":\"JavaScript is a single-threaded language and, at the same time, also non-blocking, asynchronous and concurrent. This article will explain to you how it happens.\",\"breadcrumb\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#breadcrumb\"},\"inLanguage\":\"pl-PL\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/\"]}]},{\"@type\":\"ImageObject\",\"inLanguage\":\"pl-PL\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#primaryimage\",\"url\":\"https:\\\/\\\/thecodest.co\\\/app\\\/uploads\\\/2024\\\/05\\\/cover-image-16.jpg\",\"contentUrl\":\"https:\\\/\\\/thecodest.co\\\/app\\\/uploads\\\/2024\\\/05\\\/cover-image-16.jpg\",\"width\":1920,\"height\":1080},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/blog\\\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\\\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\\\/\\\/thecodest.co\\\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Asynchronous and Single-threaded JavaScript?\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/#website\",\"url\":\"https:\\\/\\\/thecodest.co\\\/\",\"name\":\"The Codest\",\"description\":\"\",\"publisher\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\\\/\\\/thecodest.co\\\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"pl-PL\"},{\"@type\":\"Organization\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/#organization\",\"name\":\"The Codest\",\"url\":\"https:\\\/\\\/thecodest.co\\\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"pl-PL\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/#\\\/schema\\\/logo\\\/image\\\/\",\"url\":\"https:\\\/\\\/thecodest.co\\\/app\\\/uploads\\\/2024\\\/03\\\/thecodest-logo.svg\",\"contentUrl\":\"https:\\\/\\\/thecodest.co\\\/app\\\/uploads\\\/2024\\\/03\\\/thecodest-logo.svg\",\"width\":144,\"height\":36,\"caption\":\"The Codest\"},\"image\":{\"@id\":\"https:\\\/\\\/thecodest.co\\\/#\\\/schema\\\/logo\\\/image\\\/\"},\"sameAs\":[\"https:\\\/\\\/pl.linkedin.com\\\/company\\\/codest\",\"https:\\\/\\\/clutch.co\\\/profile\\\/codest\"]},{\"@type\":\"Person\",\"@id\":\"https:\\\/\\\/thecodest.co\\\/#\\\/schema\\\/person\\\/7e3fe41dfa4f4e41a7baad4c6e0d4f76\",\"name\":\"thecodest\",\"image\":{\"@type\":\"ImageObject\",\"inLanguage\":\"pl-PL\",\"@id\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/5dbfe6a1e8c86e432e8812759e34e6fe82ebac75119ae3237a6c1311fa19caf4?s=96&d=mm&r=g\",\"url\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/5dbfe6a1e8c86e432e8812759e34e6fe82ebac75119ae3237a6c1311fa19caf4?s=96&d=mm&r=g\",\"contentUrl\":\"https:\\\/\\\/secure.gravatar.com\\\/avatar\\\/5dbfe6a1e8c86e432e8812759e34e6fe82ebac75119ae3237a6c1311fa19caf4?s=96&d=mm&r=g\",\"caption\":\"thecodest\"},\"url\":\"https:\\\/\\\/thecodest.co\\\/pl\\\/author\\\/thecodest\\\/\"}]}<\/script>\n<!-- \/ Yoast SEO Premium plugin. -->","yoast_head_json":{"title":"Asynchroniczny i jednow\u0105tkowy JavaScript? - The Codest","description":"JavaScript jest j\u0119zykiem jednow\u0105tkowym, a jednocze\u015bnie nieblokuj\u0105cym, asynchronicznym i wsp\u00f3\u0142bie\u017cnym. Ten artyku\u0142 wyja\u015bni ci, jak to si\u0119 dzieje.","robots":{"index":"index","follow":"follow","max-snippet":"max-snippet:-1","max-image-preview":"max-image-preview:large","max-video-preview":"max-video-preview:-1"},"canonical":"https:\/\/thecodest.co\/pl\/blog\/asynchroniczny-i-jednowatkowy-javascript-w-petli-zdarzen\/","og_locale":"pl_PL","og_type":"article","og_title":"Asynchronous and Single-threaded JavaScript?","og_description":"JavaScript is a single-threaded language and, at the same time, also non-blocking, asynchronous and concurrent. This article will explain to you how it happens.","og_url":"https:\/\/thecodest.co\/pl\/blog\/asynchroniczny-i-jednowatkowy-javascript-w-petli-zdarzen\/","og_site_name":"The Codest","article_published_time":"2020-09-02T08:51:00+00:00","article_modified_time":"2026-04-24T11:34:04+00:00","og_image":[{"width":1920,"height":1080,"url":"https:\/\/thecodest.co\/app\/uploads\/2024\/05\/cover-image-16.jpg","type":"image\/jpeg"}],"author":"thecodest","twitter_card":"summary_large_image","twitter_misc":{"Written by":"thecodest","Est. reading time":"6 minut"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"Article","@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#article","isPartOf":{"@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/"},"author":{"name":"thecodest","@id":"https:\/\/thecodest.co\/#\/schema\/person\/7e3fe41dfa4f4e41a7baad4c6e0d4f76"},"headline":"Asynchronous and Single-threaded JavaScript?","datePublished":"2020-09-02T08:51:00+00:00","dateModified":"2026-04-24T11:34:04+00:00","mainEntityOfPage":{"@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/"},"wordCount":1058,"commentCount":0,"publisher":{"@id":"https:\/\/thecodest.co\/#organization"},"image":{"@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#primaryimage"},"thumbnailUrl":"https:\/\/thecodest.co\/app\/uploads\/2024\/05\/cover-image-16.jpg","articleSection":["Software Development"],"inLanguage":"pl-PL","potentialAction":[{"@type":"CommentAction","name":"Comment","target":["https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#respond"]}]},{"@type":"WebPage","@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/","url":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/","name":"Asynchroniczny i jednow\u0105tkowy JavaScript? - The Codest","isPartOf":{"@id":"https:\/\/thecodest.co\/#website"},"primaryImageOfPage":{"@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#primaryimage"},"image":{"@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#primaryimage"},"thumbnailUrl":"https:\/\/thecodest.co\/app\/uploads\/2024\/05\/cover-image-16.jpg","datePublished":"2020-09-02T08:51:00+00:00","dateModified":"2026-04-24T11:34:04+00:00","description":"JavaScript jest j\u0119zykiem jednow\u0105tkowym, a jednocze\u015bnie nieblokuj\u0105cym, asynchronicznym i wsp\u00f3\u0142bie\u017cnym. Ten artyku\u0142 wyja\u015bni ci, jak to si\u0119 dzieje.","breadcrumb":{"@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#breadcrumb"},"inLanguage":"pl-PL","potentialAction":[{"@type":"ReadAction","target":["https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/"]}]},{"@type":"ImageObject","inLanguage":"pl-PL","@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#primaryimage","url":"https:\/\/thecodest.co\/app\/uploads\/2024\/05\/cover-image-16.jpg","contentUrl":"https:\/\/thecodest.co\/app\/uploads\/2024\/05\/cover-image-16.jpg","width":1920,"height":1080},{"@type":"BreadcrumbList","@id":"https:\/\/thecodest.co\/blog\/asynchronous-and-single-threaded-javascript-meet-the-event-loop\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/thecodest.co\/"},{"@type":"ListItem","position":2,"name":"Asynchronous and Single-threaded JavaScript?"}]},{"@type":"WebSite","@id":"https:\/\/thecodest.co\/#website","url":"https:\/\/thecodest.co\/","name":"The Codest","description":"","publisher":{"@id":"https:\/\/thecodest.co\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/thecodest.co\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"pl-PL"},{"@type":"Organization","@id":"https:\/\/thecodest.co\/#organization","name":"The Codest","url":"https:\/\/thecodest.co\/","logo":{"@type":"ImageObject","inLanguage":"pl-PL","@id":"https:\/\/thecodest.co\/#\/schema\/logo\/image\/","url":"https:\/\/thecodest.co\/app\/uploads\/2024\/03\/thecodest-logo.svg","contentUrl":"https:\/\/thecodest.co\/app\/uploads\/2024\/03\/thecodest-logo.svg","width":144,"height":36,"caption":"The Codest"},"image":{"@id":"https:\/\/thecodest.co\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/pl.linkedin.com\/company\/codest","https:\/\/clutch.co\/profile\/codest"]},{"@type":"Person","@id":"https:\/\/thecodest.co\/#\/schema\/person\/7e3fe41dfa4f4e41a7baad4c6e0d4f76","name":"thecodest","image":{"@type":"ImageObject","inLanguage":"pl-PL","@id":"https:\/\/secure.gravatar.com\/avatar\/5dbfe6a1e8c86e432e8812759e34e6fe82ebac75119ae3237a6c1311fa19caf4?s=96&d=mm&r=g","url":"https:\/\/secure.gravatar.com\/avatar\/5dbfe6a1e8c86e432e8812759e34e6fe82ebac75119ae3237a6c1311fa19caf4?s=96&d=mm&r=g","contentUrl":"https:\/\/secure.gravatar.com\/avatar\/5dbfe6a1e8c86e432e8812759e34e6fe82ebac75119ae3237a6c1311fa19caf4?s=96&d=mm&r=g","caption":"thecodest"},"url":"https:\/\/thecodest.co\/pl\/author\/thecodest\/"}]}},"_links":{"self":[{"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/posts\/3044","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/comments?post=3044"}],"version-history":[{"count":6,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/posts\/3044\/revisions"}],"predecessor-version":[{"id":7721,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/posts\/3044\/revisions\/7721"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/media\/3045"}],"wp:attachment":[{"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/media?parent=3044"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/categories?post=3044"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/thecodest.co\/pl\/wp-json\/wp\/v2\/tags?post=3044"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}