chrome-page-eval

Evaluate a script function on a page with Chrome

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Version published: 8 months ago

Weekly downloads: 3.5K; increased by10.01%

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Created: 7 years ago

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chrome-page-eval

Evaluate a script function on a page with Chrome

This module let you evaluate a script function on a page using Chrome (controlled with puppeteer) and get the return value of the evaluation in node.

Usage

<!-- sample.html -->
<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>Test page</title>
</head>
<body>
  <div class="content">1</div>
  <div class="content">2</div>
  <div class="content">3</div>
  <div class="content">4</div>
</body>
</html>

const puppeteer = require('puppeteer')
const chromePageEval = require('chrome-page-eval')
const chromeEval = chromePageEval({ puppeteer })

(async () => {
  try {
    const result = await chromeEval({
      html: '/path/to/sample.html',
      scriptFn: `
        function () {
          let title = document.title

          let content = Array.from(document.querySelectorAll('.content'), (node) => {
            return node.textContent
          })

          return {
            title,
            content
          }
        }
      `
    })

    console.log(result.title) // -> Test page
    console.log(result.content) // -> [1, 2, 3, 4]
  } catch (e) {
    console.error('Error while trying to evaluate script:', e)
  }
})()

Constructor options

const chromePageEval = require('chrome-page-eval')
const chromeEval = chromePageEval({ /*[constructor options here]*/ })

puppeteer [required] - the exported module from puppeteer that your app is going to use
properties with any of the launch options supported by puppeteer

Evaluate options

const puppeteer = require('puppeteer')
const chromePageEval = require('chrome-page-eval')
const chromeEval = chromePageEval({ puppeteer })

(async () => {
  const result = await chromeEval({ /*[evaluate options here]*/ })
})()

html string [required] - the path to the html file to load in a Chrome page
scriptFn string [required] - the script to evaluate in the Chrome page. the script must be a function that returns a value. ex: scriptFn: 'function () { return 1 + 2}'
viewport object - object with any of the viewport options supported by puppeteer
args array - a list of custom arguments to pass to the scriptFn function. ex: args: [1, 2] and with scriptFn: function (a, b) { return a + b}' will produce 3 as result
styles array - array of css strings to insert at the beginning of page's head element. ex: styles: ['* { font-family: 'Calibri'; font-size: 16px; }']
waitForJS boolean - when true the scriptFn won't be executed until the variable specified in waitForJSVarName option is set to true in page's javscript. defaults to false
waitForJSVarName string - name of the variable that will be used as trigger of scriptFn. defaults to "CHROME_PAGE_EVAL_READY"
waitUntil string - a value that specifies when a page is considered to be loaded, for the list of all possible values and its meanings see waitUntil option in puppeteer docs. defaults to the the default value of puppeteer
timeout number - time in ms to wait for the script evaluation to complete, when the timeout is reached the evaluation is cancelled. defaults to 30000

Requirements

Install puppeteer >= 1.0.0 with npm install puppeteer --save in your project and pass it to chrome-page-eval constructor function.

Caveats

What you return in your script function (scriptFn option) must be a serializable value in order to receive it properly, if a non serializable value is returned you will get undefined as the result.

Debugging

To get more information (internal debugging logs of the module) about what's happening during the evaluation on the page start your app in this way: DEBUG=chrome-page-eval* node [your-entry-file-here].js (on Windows use set DEBUG=chrome-page-eval* && node [your-entry-file-here].js). This will print out to the console some additional information about what's going on.
To see the Chrome instance created (the visible chrome window) run your app with the CHROME_PAGE_EVAL_DEBUGGING env var: CHROME_PAGE_EVAL_DEBUGGING=true node [your-entry-file-here].js (on Windows use set CHROME_PAGE_EVAL_DEBUGGING=true && node [your-entry-file-here].js).

License

See license

Keywords

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Package last updated on 14 Mar 2024

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