puppeteer/assets/js/906a64cf.231b2d30.js

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context.",source:"@site/versioned_docs/version-21.3.2/api/puppeteer.page.waitforfunction.md",sourceDirName:"api",slug:"/api/puppeteer.page.waitforfunction",permalink:"/api/puppeteer.page.waitforfunction",draft:!1,tags:[],version:"21.3.2",frontMatter:{sidebar_label:"Page.waitForFunction"},sidebar:"api",previous:{title:"Page.waitForFrame",permalink:"/api/puppeteer.page.waitforframe"},next:{title:"Page.waitForNavigation",permalink:"/api/puppeteer.page.waitfornavigation"}},u={},c=[{value:"Signature:",id:"signature",level:4},{value:"Parameters",id:"parameters",level:2},{value:"Example 1",id:"example-1",level:2},{value:"Example 2",id:"example-2",level:2},{value:"Example 3",id:"example-3",level:2}],s={toc:c};function m(e){var{components:t}=e,n=o(e,["components"]);return(0,a.kt)("wrapper",r({},s,n,{components:t,mdxType:"MDXLayout"}),(0,a.kt)("h1",r({},{id:"pagewaitforfunction-method"}),"Page.waitForFunction() method"),(0,a.kt)("p",null,"Waits for a function to finish evaluating in the page's context."),(0,a.kt)("h4",r({},{id:"signature"}),"Signature:"),(0,a.kt)("pre",null,(0,a.kt)("code",r({parentName:"pre"},{className:"language-typescript"}),"class Page {\n  waitForFunction<\n    Params extends unknown[],\n    Func extends EvaluateFunc<Params> = EvaluateFunc<Params>,\n  >(\n    pageFunction: Func | string,\n    options?: FrameWaitForFunctionOptions,\n    ...args: Params\n  ): Promise<HandleFor<Awaited<ReturnType<Func>>>>;\n}\n")),(0,a.kt)("h2",r({},{id:"parameters"}),"Parameters"),(0,a.kt)("table",null,(0,a.kt)("thead",{parentName:"table"},(0,a.kt)("tr",{parentName:"thead"},(0,a.kt)("th",r({parentName:"tr"},{align:null}),"Parameter"),(0,a.kt)("th",r({parentName:"tr"},{align:null}),"Type"),(0,a.kt)("th",r({parentName:"tr"},{align:null}),"Description"))),(0,a.kt)("tbody",{parentName:"table"},(0,a.kt)("tr",{parentName:"tbody"},(0,a.kt)("td",r({parentName:"tr"},{align:null}),"pageFunction"),(0,a.kt)("td",r({parentName:"tr"},{align:null}),"Func ","|"," string"),(0,a.kt)("td",r({parentName:"tr"},{align:null}),"Function to be evaluated in browser context")),(0,a.kt)("tr",{parentName:"tbody"},(0,a.kt)("td",r({parentName:"tr"},{align:null}),"options"),(0,a.kt)("td",r({parentName:"tr"},{align:null}),(0,a.kt)("a",r({parentName:"td"},{href:"/api/puppeteer.framewaitforfunctionoptions"}),"FrameWaitForFunctionOptions")),(0,a.kt)("td",r({parentName:"tr"},{align:null}),(0,a.kt)("em",{parentName:"td"},"(Optional)")," Options for configuring waiting behavior.")),(0,a.kt)("tr",{parentName:"tbody"},(0,a.kt)("td",r({parentName:"tr"},{align:null}),"args"),(0,a.kt)("td",r({parentName:"tr"},{align:null}),"Params"),(0,a.kt)("td",r({parentName:"tr"},{align:null}))))),(0,a.kt)("p",null,(0,a.kt)("strong",{parentName:"p"},"Returns:")),(0,a.kt)("p",null,"Promise","<",(0,a.kt)("a",r({parentName:"p"},{href:"/api/puppeteer.handlefor"}),"HandleFor"),"<","Awaited","<","ReturnType","<","Func",">",">",">",">"),(0,a.kt)("h2",r({},{id:"example-1"}),"Example 1"),(0,a.kt)("p",null,"The ",(0,a.kt)("a",r({parentName:"p"},{href:"/api/puppeteer.page.waitforfunction"}),"Page.waitForFunction()")," can be used to observe viewport size change:"),(0,a.kt)("pre",null,(0,a.kt)("code",r({parentName:"pre"},{className:"language-ts"}),"import puppeteer from 'puppeteer';\n(async () => {\n  const browser = await puppeteer.launch();\n  const page = await browser.newPage();\n  const watchDog = page.waitForFunction('window.innerWidth < 100');\n  await page.setViewport({width: 50, height: 50});\n  await watchDog;\n  await browser.close();\n})();\n")),(0,a.kt)("h2",r({},{id:"example-2"}),"Example 2"),(0,a.kt)("p",null,"To pass arguments from node.js to the predicate of ",(0,a.kt)("a",r({parentName:"p"},{href:"/api/puppeteer.page.waitforfunction"}),"Page.waitForFunction()")," function:"),(0,a.kt)("pre",null,(0,a.kt)("code",r({parentName:"pre"},{className:"language-ts"}),"const selector = '.foo';\nawait page.waitForFunction(\n  selector => !!document.querySelector(selector),\n  {},\n  selector\n);\n")),(0,a.kt)("h2",r({},{id:"example-3"}),"Example 3"),(0,a.kt)("p",null,"The predicate of ",(0,a.kt)("a",r({parentName:"p"},{href:"/api/puppeteer.page.waitforfunction"}),"Page.waitForFunction()")," can be asynchronous too:"),(0,a.kt)("pre",null,(0,a.kt)("code",r({parentName:"pre"},{className:"language-ts"}),"const username = 'github-username';\nawait page.waitForFunction(\n  async username => {\n    const githubResponse = await fetch(\n      `https://api.github.com/users/${username}`\n    );\n    const githubUser = await githubResponse.json();\n    // show the avatar\n    const img = document.createElement('img');\n    img.src = githubUser.avatar_url;\n    // wait 3 seconds\n    await new Promise((resolve, reject) => setTimeout(resolve, 3000));\n    img.remove();\n  },\n  {},\n  username\n);\n")))}m.isMDXComponent=!0}}]);