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When called, the function executes ",(0,r.kt)("inlineCode",{parentName:"p"},"puppeteerFunction")," in node.js and returns a ",(0,r.kt)("inlineCode",{parentName:"p"},"Promise")," which resolves to the return value of ",(0,r.kt)("inlineCode",{parentName:"p"},"puppeteerFunction"),"."),(0,r.kt)("p",null,"If the puppeteerFunction returns a ",(0,r.kt)("inlineCode",{parentName:"p"},"Promise"),", it will be awaited."),(0,r.kt)("admonition",a({},{type:"note"}),(0,r.kt)("p",{parentName:"admonition"},"Functions installed via ",(0,r.kt)("inlineCode",{parentName:"p"},"page.exposeFunction")," survive navigations.")),(0,r.kt)("h4",a({},{id:"signature"}),"Signature:"),(0,r.kt)("pre",null,(0,r.kt)("code",a({parentName:"pre"},{className:"language-typescript"}),"class Page {\n  exposeFunction(\n    name: string,\n    pptrFunction:\n      | Function\n      | {\n          default: Function;\n        }\n  ): Promise<void>;\n}\n")),(0,r.kt)("h2",a({},{id:"parameters"}),"Parameters"),(0,r.kt)("table",null,(0,r.kt)("thead",{parentName:"table"},(0,r.kt)("tr",{parentName:"thead"},(0,r.kt)("th",a({parentName:"tr"},{align:null}),"Parameter"),(0,r.kt)("th",a({parentName:"tr"},{align:null}),"Type"),(0,r.kt)("th",a({parentName:"tr"},{align:null}),"Description"))),(0,r.kt)("tbody",{parentName:"table"},(0,r.kt)("tr",{parentName:"tbody"},(0,r.kt)("td",a({parentName:"tr"},{align:null}),"name"),(0,r.kt)("td",a({parentName:"tr"},{align:null}),"string"),(0,r.kt)("td",a({parentName:"tr"},{align:null}),"Name of the function on the window object")),(0,r.kt)("tr",{parentName:"tbody"},(0,r.kt)("td",a({parentName:"tr"},{align:null}),"pptrFunction"),(0,r.kt)("td",a({parentName:"tr"},{align:null}),"Function ","|"," { default: Function; }"),(0,r.kt)("td",a({parentName:"tr"},{align:null}),"Callback function which will be called in Puppeteer's context.")))),(0,r.kt)("p",null,(0,r.kt)("strong",{parentName:"p"},"Returns:")),(0,r.kt)("p",null,"Promise","<","void",">"),(0,r.kt)("h2",a({},{id:"example-1"}),"Example 1"),(0,r.kt)("p",null,"An example of adding an ",(0,r.kt)("inlineCode",{parentName:"p"},"md5")," function into the page:"),(0,r.kt)("pre",null,(0,r.kt)("code",a({parentName:"pre"},{className:"language-ts"}),"import puppeteer from 'puppeteer';\nimport crypto from 'crypto';\n\n(async () => {\n  const browser = await puppeteer.launch();\n  const page = await browser.newPage();\n  page.on('console', msg => console.log(msg.text()));\n  await page.exposeFunction('md5', text =>\n    crypto.createHash('md5').update(text).digest('hex')\n  );\n  await page.evaluate(async () => {\n    // use window.md5 to compute hashes\n    const myString = 'PUPPETEER';\n    const myHash = await window.md5(myString);\n    console.log(`md5 of ${myString} is ${myHash}`);\n  });\n  await browser.close();\n})();\n")),(0,r.kt)("h2",a({},{id:"example-2"}),"Example 2"),(0,r.kt)("p",null,"An example of adding a ",(0,r.kt)("inlineCode",{parentName:"p"},"window.readfile")," function into the page:"),(0,r.kt)("pre",null,(0,r.kt)("code",a({parentName:"pre"},{className:"language-ts"}),"import puppeteer from 'puppeteer';\nimport fs from 'fs';\n\n(async () => {\n  const browser = await puppeteer.launch();\n  const page = await browser.newPage();\n  page.on('console', msg => console.log(msg.text()));\n  await page.exposeFunction('readfile', async filePath => {\n    return new Promise((resolve, reject) => {\n      fs.readFile(filePath, 'utf8', (err, text) => {\n        if (err) reject(err);\n        else resolve(text);\n      });\n    });\n  });\n  await page.evaluate(async () => {\n    // use window.readfile to read contents of a file\n    const content = await window.readfile('/etc/hosts');\n    console.log(content);\n  });\n  await browser.close();\n})();\n")))}m.isMDXComponent=!0}}]);