Phantom.js 中的 setTimeout

问题描述

下面的代码希望 Phantom.js 加载页面，点击按钮并等待 5 秒钟，然后返回页面的 HTML 代码.

The code below wants Phantom.js to load the page, click on a button and wait for 5 seconds before returning the page's HTML code.

问题:但是使用 setTimeout() 来创建 5 秒延迟会导致page.evaluate 函数将 null 返回给回调函数而不是 HTML.

Problem: However using setTimeout() to create the 5 seconds delay causes thepage.evaluate function to return null to the callback function instead of the HTML.

myUrl = 'http://www.google.com'

var phantom = Meteor.npmRequire('phantom')
phantom.create = Meteor.wrapAsync(phantom.create)
phantom.create( function(ph) {

    ph.createPage = Meteor.wrapAsync(ph.createPage)
    ph.createPage(function(page) {

        page.open = Meteor.wrapAsync(page.open)
        page.open(listingUrl, function(status) {
            console.log('Page loaded')

            page.evaluate = Meteor.wrapAsync(page.evaluate)
            page.evaluate(function() {

                // Find the button
                var element = document.querySelector( '.search-btn' );

                // create a mouse click event
                var event = document.createEvent( 'MouseEvents' );
                event.initMouseEvent( 'click', true, true, window, 1, 0, 0 );

                // send click to element
                element.dispatchEvent( event );

                // Give page time to process Click event
                setTimeout(function() {
                    // Return HTML code
                    return document.documentElement.outerHTML
                }, 5000)

            }, function(html) {

                // html is `null`
                doSomething()

            })
        })
    })
})

用 Meteor.setTimeout() 替换 setTimeout() 会导致另一个错误:

Replacing setTimeout() with Meteor.setTimeout() causes another error:

phantom stdout: ReferenceError: Can't find variable: Meteor

推荐答案

page.evaluate() 是 PhantomJS 的沙盒页面上下文.它无法访问外部定义的变量.如果您需要超时，那么您需要对 page.evaluate() 进行两次调用，因为您无法从异步函数返回任何内容(说明):

page.evaluate() is the sandboxed page context of PhantomJS. It has no access to variables defined on the outside. If you need the timeout, then you need to do two calls to page.evaluate(), because you cannot return anything from a asynchronous function (explanation):

page.evaluate(function() {
    ...
    element.dispatchEvent( event );
}, function() {
    setTimeout(function() {
        page.evaluate(function() {
            return document.documentElement.outerHTML
        }, function(html) {
            doSomething()
        })
    }, 5000)
})

您可以通过直接访问定义的内容来缩短代码，而不是使用第二个 page.evaluate() 调用这里:

Instead of using the second page.evaluate() call, you may shorten the code by directly accessing the content as defined here:

setTimeout(function() {
    page.get("content", function(content) {
        doSomething()
    })
}, 5000)

这篇关于Phantom.js 中的 setTimeout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！