如何在Puppeteer page.$ eval中传递函数/变量? [英] How to pass a function / variable in Puppeteer page.$eval?

问题描述

我正在使用Puppeteer自动填写Web表单.每次[input]字段中的名称应更改为与数组不同的名称.

I am using Puppeteer to automatically fill a webform. Each time the name in the [input] field should change to a different name from an array.

如果我直接在页面中分配了一个名称.$ eval函数(例如"Michael")一切正常.

If I assign a name directly in the page.$eval function (e.g. "Michael") everything works as expected.

   puppeteer.launch({ headless: false }).then(async browser => {
   const page = await browser.newPage()
   await page.goto('https://example.com/webform')
       
   await page.waitFor('input[name=name]');
   await page.$eval('input[name=name]', (el) => el.value = "Michael");

但是一旦我尝试传递变量或函数(例如name_from_array)

But as soon as I try to pass a variable or function (e.g. name_from_array)

var name = ["Michael", "Lisa", "Jason"]
const random = Math.floor(Math.random() * name.length);
var name_from_array = name[random];

puppeteer.launch({ headless: false }).then(async browser => {
const page = await browser.newPage()
await page.goto('https://example.com/webform')
   
await page.waitFor('input[name=name]');
await page.$eval('input[name=name]', (el) => el.value = name_from_array);

我收到一条错误消息，提示"UnhandledPromiseRejectionWarning:错误:评估失败:ReferenceError:未定义name_from_array".

I get an error message saying "UnhandledPromiseRejectionWarning: Error: Evaluation failed: ReferenceError: name_from_array is not defined".

您知道如何解决此问题吗?

Any idea how to fix this issue?

非常感谢！

推荐答案

通过阅读

By reading the puppeteer's documentation, you can see where we can insert parameters.

我们可以看到参数是最后收到的数组(... args).

We can see that the parameters are a spreaded array (...args) that is received in last.

page.$eval(selector, pageFunction[, ...args])

因此，我们传递 selector ，然后传递要评估的函数 pageFunction ，最后传递 pageFunction 的参数，传递 ...args .

So we pass the selector then the function to be evaluated pageFunction and finally the arguments to the pageFunction the ...args.

await page.$eval('input[name=name]', (el, name) => { 
   el.value = name
}, name);

• el 是与 document.querySelector('input [name = name]')
等效的元素
• name 是您的参数，它将接收 names_for_array (或您想要的任何内容)
• 最后，您将值传递给参数 name
• el is your element equivalent to document.querySelector('input[name=name]')
• name is your parameter that will receive the names_for_array (or anything you want)
• And lastly you pass the value to the parameter name

您可以传递任何所需的内容，因为 name 是一个参数.示例:

You can pass anything you want because name is a parameter. Example:

await page.$eval('input[name=name]', (el, name) => { 
   el.value = name
}, 'Michael');

这篇关于如何在Puppeteer page.$ eval中传递函数/变量?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！