{"id":72662,"date":"2020-01-14T16:36:18","date_gmt":"2020-01-14T11:06:18","guid":{"rendered":"https:\/\/www.vskills.in\/certification\/tutorial\/?p=72662"},"modified":"2024-04-12T14:22:58","modified_gmt":"2024-04-12T08:52:58","slug":"cycles","status":"publish","type":"page","link":"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/","title":{"rendered":"Cycles"},"content":{"rendered":"

When there are circular require() calls, a module might not have finished executing when it is returned. Consider this situation:<\/span><\/p>\n

\u00a0<\/span>a.js:<\/span><\/p>\n

console.log(‘a starting’);<\/span><\/p>\n

exports.done = false;<\/span><\/p>\n

const b = require(‘.\/b.js’);<\/span><\/p>\n

console.log(‘in a, b.done = %j’, b.done);<\/span><\/p>\n

exports.done = true;<\/span><\/p>\n

console.log(‘a done’);<\/span><\/p>\n

\u00a0<\/span>b.js:<\/span><\/p>\n

console.log(‘b starting’);<\/span><\/p>\n

exports.done = false;<\/span><\/p>\n

const a = require(‘.\/a.js’);<\/span><\/p>\n

console.log(‘in b, a.done = %j’, a.done);<\/span><\/p>\n

exports.done = true;<\/span><\/p>\n

console.log(‘b done’);<\/span><\/p>\n

\u00a0<\/span>main.js:<\/span><\/p>\n

console.log(‘main starting’);<\/span><\/p>\n

const a = require(‘.\/a.js’);<\/span><\/p>\n

const b = require(‘.\/b.js’);<\/span><\/p>\n

console.log(‘in main, a.done = %j, b.done = %j’, a.done, b.done);<\/span><\/p>\n

\u00a0<\/span>When main.js loads a.js, then a.js in turn loads b.js. At that point, b.js tries to load a.js. In order to prevent an infinite loop, an unfinished copy of the a.js exports object is returned to the b.js module. b.js then finishes loading, and its exports object is provided to the a.js module.<\/span><\/p>\n

\u00a0<\/span>By the time main.js has loaded both modules, they’re both finished. The output of this program would thus be:<\/span><\/p>\n

\u00a0<\/span>$ node main.js<\/span><\/p>\n

main starting<\/span><\/p>\n

a starting<\/span><\/p>\n

b starting<\/span><\/p>\n

in b, a.done = false<\/span><\/p>\n

b done<\/span><\/p>\n

in a, b.done = true<\/span><\/p>\n

a done<\/span><\/p>\n

in main, a.done = true, b.done = true<\/span><\/p>\n

\u00a0<\/span>Careful planning is required to allow cyclic module dependencies to work correctly within an application.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

When there are circular require() calls, a module might not have finished executing when it is returned. Consider this situation: \u00a0a.js: console.log(‘a starting’); exports.done = false; const b = require(‘.\/b.js’); console.log(‘in a, b.done = %j’, b.done); exports.done = true; console.log(‘a done’); \u00a0b.js: console.log(‘b starting’); exports.done = false; const a = require(‘.\/a.js’); console.log(‘in b, a.done =…<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"categories":[8453],"tags":[8478],"class_list":["post-72662","page","type-page","status-publish","hentry","category-node-js","tag-cycles"],"acf":[],"yoast_head":"\nCycles - Tutorial<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Cycles - Tutorial\" \/>\n<meta property=\"og:description\" content=\"When there are circular require() calls, a module might not have finished executing when it is returned. Consider this situation: \u00a0a.js: console.log(‘a starting’); exports.done = false; const b = require(‘.\/b.js’); console.log(‘in a, b.done = %j’, b.done); exports.done = true; console.log(‘a done’); \u00a0b.js: console.log(‘b starting’); exports.done = false; const a = require(‘.\/a.js’); console.log(‘in b, a.done =...\" \/>\n<meta property=\"og:url\" content=\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/\" \/>\n<meta property=\"og:site_name\" content=\"Tutorial\" \/>\n<meta property=\"article:publisher\" content=\"https:\/\/www.facebook.com\/vskills.in\/\" \/>\n<meta property=\"article:modified_time\" content=\"2024-04-12T08:52:58+00:00\" \/>\n<meta name=\"twitter:label1\" content=\"Est. reading time\" \/>\n\t<meta name=\"twitter:data1\" content=\"1 minute\" \/>\n<script type=\"application\/ld+json\" class=\"yoast-schema-graph\">{\"@context\":\"https:\/\/schema.org\",\"@graph\":[{\"@type\":\"WebPage\",\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/\",\"url\":\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/\",\"name\":\"Cycles - Tutorial\",\"isPartOf\":{\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/#website\"},\"datePublished\":\"2020-01-14T11:06:18+00:00\",\"dateModified\":\"2024-04-12T08:52:58+00:00\",\"breadcrumb\":{\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/#breadcrumb\"},\"inLanguage\":\"en-US\",\"potentialAction\":[{\"@type\":\"ReadAction\",\"target\":[\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/\"]}]},{\"@type\":\"BreadcrumbList\",\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/#breadcrumb\",\"itemListElement\":[{\"@type\":\"ListItem\",\"position\":1,\"name\":\"Home\",\"item\":\"https:\/\/www.vskills.in\/certification\/tutorial\/\"},{\"@type\":\"ListItem\",\"position\":2,\"name\":\"Cycles\"}]},{\"@type\":\"WebSite\",\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/#website\",\"url\":\"https:\/\/www.vskills.in\/certification\/tutorial\/\",\"name\":\"Tutorial\",\"description\":\"Vskills - A initiative in elearning and certification\",\"publisher\":{\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/#organization\"},\"potentialAction\":[{\"@type\":\"SearchAction\",\"target\":{\"@type\":\"EntryPoint\",\"urlTemplate\":\"https:\/\/www.vskills.in\/certification\/tutorial\/?s={search_term_string}\"},\"query-input\":{\"@type\":\"PropertyValueSpecification\",\"valueRequired\":true,\"valueName\":\"search_term_string\"}}],\"inLanguage\":\"en-US\"},{\"@type\":\"Organization\",\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/#organization\",\"name\":\"Vskills\",\"url\":\"https:\/\/www.vskills.in\/certification\/tutorial\/\",\"logo\":{\"@type\":\"ImageObject\",\"inLanguage\":\"en-US\",\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/#\/schema\/logo\/image\/\",\"url\":\"https:\/\/www.vskills.in\/certification\/tutorial\/wp-content\/uploads\/2017\/07\/vskills-min-logo.jpg\",\"contentUrl\":\"https:\/\/www.vskills.in\/certification\/tutorial\/wp-content\/uploads\/2017\/07\/vskills-min-logo.jpg\",\"width\":73,\"height\":55,\"caption\":\"Vskills\"},\"image\":{\"@id\":\"https:\/\/www.vskills.in\/certification\/tutorial\/#\/schema\/logo\/image\/\"},\"sameAs\":[\"https:\/\/www.facebook.com\/vskills.in\/\",\"https:\/\/x.com\/vskills_in\",\"https:\/\/www.linkedin.com\/company-beta\/1371554\/\",\"https:\/\/www.youtube.com\/channel\/UCMWnscxPwRF_PqXo9B7q_Tw\"]}]}<\/script>\n<!-- \/ Yoast SEO plugin. -->","yoast_head_json":{"title":"Cycles - Tutorial","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:\/\/www.vskills.in\/certification\/tutorial\/cycles\/","og_locale":"en_US","og_type":"article","og_title":"Cycles - Tutorial","og_description":"When there are circular require() calls, a module might not have finished executing when it is returned. Consider this situation: \u00a0a.js: console.log(‘a starting’); exports.done = false; const b = require(‘.\/b.js’); console.log(‘in a, b.done = %j’, b.done); exports.done = true; console.log(‘a done’); \u00a0b.js: console.log(‘b starting’); exports.done = false; const a = require(‘.\/a.js’); console.log(‘in b, a.done =...","og_url":"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/","og_site_name":"Tutorial","article_publisher":"https:\/\/www.facebook.com\/vskills.in\/","article_modified_time":"2024-04-12T08:52:58+00:00","twitter_misc":{"Est. reading time":"1 minute"},"schema":{"@context":"https:\/\/schema.org","@graph":[{"@type":"WebPage","@id":"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/","url":"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/","name":"Cycles - Tutorial","isPartOf":{"@id":"https:\/\/www.vskills.in\/certification\/tutorial\/#website"},"datePublished":"2020-01-14T11:06:18+00:00","dateModified":"2024-04-12T08:52:58+00:00","breadcrumb":{"@id":"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/#breadcrumb"},"inLanguage":"en-US","potentialAction":[{"@type":"ReadAction","target":["https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/"]}]},{"@type":"BreadcrumbList","@id":"https:\/\/www.vskills.in\/certification\/tutorial\/cycles\/#breadcrumb","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https:\/\/www.vskills.in\/certification\/tutorial\/"},{"@type":"ListItem","position":2,"name":"Cycles"}]},{"@type":"WebSite","@id":"https:\/\/www.vskills.in\/certification\/tutorial\/#website","url":"https:\/\/www.vskills.in\/certification\/tutorial\/","name":"Tutorial","description":"Vskills - A initiative in elearning and certification","publisher":{"@id":"https:\/\/www.vskills.in\/certification\/tutorial\/#organization"},"potentialAction":[{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https:\/\/www.vskills.in\/certification\/tutorial\/?s={search_term_string}"},"query-input":{"@type":"PropertyValueSpecification","valueRequired":true,"valueName":"search_term_string"}}],"inLanguage":"en-US"},{"@type":"Organization","@id":"https:\/\/www.vskills.in\/certification\/tutorial\/#organization","name":"Vskills","url":"https:\/\/www.vskills.in\/certification\/tutorial\/","logo":{"@type":"ImageObject","inLanguage":"en-US","@id":"https:\/\/www.vskills.in\/certification\/tutorial\/#\/schema\/logo\/image\/","url":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-content\/uploads\/2017\/07\/vskills-min-logo.jpg","contentUrl":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-content\/uploads\/2017\/07\/vskills-min-logo.jpg","width":73,"height":55,"caption":"Vskills"},"image":{"@id":"https:\/\/www.vskills.in\/certification\/tutorial\/#\/schema\/logo\/image\/"},"sameAs":["https:\/\/www.facebook.com\/vskills.in\/","https:\/\/x.com\/vskills_in","https:\/\/www.linkedin.com\/company-beta\/1371554\/","https:\/\/www.youtube.com\/channel\/UCMWnscxPwRF_PqXo9B7q_Tw"]}]}},"_links":{"self":[{"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/pages\/72662","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/comments?post=72662"}],"version-history":[{"count":3,"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/pages\/72662\/revisions"}],"predecessor-version":[{"id":73174,"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/pages\/72662\/revisions\/73174"}],"wp:attachment":[{"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/media?parent=72662"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/categories?post=72662"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vskills.in\/certification\/tutorial\/wp-json\/wp\/v2\/tags?post=72662"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}