casperJS how to click multiple links in a table wh

问题:

I want to scrape some web data using CasperJS. The data is in a table, in each row there is a link leading to a page with more detail. In the script there is a loop iterating through all table rows. I want Casper to click the link, collect the data on a sub-page and come one history step back to process next table row. The problem is that the click() doesn't work and I don't know why. Is there any way to fix this ? (note: a javascript function viewContact is invoked by href)

Here is the code :

var employee = {
    last_name: "",
    first_name: "",
    position: "",
    department: "",
    location: "",
    email: "",
    phone: "",
    twitter: ""
};

var employees = [];
var result_number = 50;
var start_url = 'https://www.jigsaw.com/SearchContact.xhtml?companyId=489781&orderby=0&order=0&opCode=paging&mode=0&estimatedCount=126&dead=false&rpage=1&rowsPerPage=200';

var casper = require('casper').create({
    javascriptEnabled: true
});

casper.start(start_url, function() {
    var js = this.evaluate(function() {
    return document;
});

     for (var i = 1; i <= result_number; i++)
     {        
        // j stands for three neighbour td columns containing: 
        // position, name+link, location

        employee.position = this.getHTML('#sortableTable tr:nth-child(' + i + ') td:nth-child(3) span');

        // click link and get other data
        this.click('#sortableTable tr:nth-child(' + i + ') td:nth-child(4) span a');
            employee.first_name = this.getHTML('#sortableTable tr:nth-child(' + i + ') td:nth-child(4) span a');

        //collect data
        this.waitForSelector('#firstname', function() {
            employee.first_name = this.getHTML('#firstname');
        });

        this.waitForSelector('#lastname', function() {
            employee.last_name = this.getHTML('#lastname');
        });
        this.waitForSelector('#state', function() {
            employee.department = this.getHTML('#state');
        });
        this.waitForSelector('#email', function() {
            employee.email = this.getHTML('#email');
        });
        this.waitForSelector('#phone', function() {
            employee.phone = this.getHTML('#phone');
        });

        //get back to previous page
        this.back();

        employee.location = this.getHTML('#sortableTable tr:nth-child(' + i + ') td:nth-child(5) span');

        this.echo('\n\n Employee number: ' + i + " :\n");
        this.echo('first name : ' + employee.first_name);
        this.echo('last name  : ' + employee.last_name);
        this.echo('position   : ' + employee.position);
        this.echo('department : ' + employee.department);
        this.echo('location   : ' + employee.location);
        this.echo('email      : ' + employee.email);
        this.echo('phone      : ' + employee.phone);

}

});

casper.run();

回答1:

I see two things here that need to be corrected. First, The for loop in your code doesn't appear to be in the scope of any casperjs methods.

This:

for (var i = 1; i <= result_number; i++)

It should be inside a casper.then method. I notice you have the closing brackets so perhaps you've posted code by copy pasting it in a sloppy manner.

Secondly and most importantly, the tr:nth-child(' + i + ') you'd like to interact with won't work in this way. I don't know why but it doesn't seem to work this straight forwardly. I've tried to do the same thing. My solution was to first of all convert the i to a string instead of a number like so:

pageturn = pageturn + 1;
// Collect <td> contents on each page.
var pageturnString = pageturn.toString();
var linknum = 'a.SomeLinkClass:nth-child('+pageturnString+')';

in my case I'm using this to click to change the page, either way you must encapsulate your interaction with the said css selector inside a this.then() method inside the first method, and then a second child method does the rest of the for loop.

Example:

casper.each(pagecount, function() {
    this.then(function() {
        pageturn = pageturn + 1;
        // Collect <td> contents on each page.
        var pageturnString = pageturn.toString();
        var linknum = 'a.SomeLinkClass:nth-child('+pageturnString+')';
    });

    this.then(function() {
        //Now run for loop here. 
    });
 });

If you don't encapsulate the css selector construction within the this.then() method before it's used in the next method, it won't work. I don't know why but that's the deal. In my code, pagecount could possibly be used instead of your for loop but I'll leave that up to you.

回答2:

I've got a page where I'm seeing this in Casper:

[debug] [phantom] Mouse event 'mousedown' on selector: tr:nth-child(2) a CasperError: Cannot dispatch mousedown event on nonexistent selector: tr:nth-child(2) a

As this error is caused by a failed exists, which relies on querySelectorAll, I've played around with that and found that the following sets x2 to null (although x1 isn't null):

this.evaluate(function() {
    var x1 = document.querySelector('tr:nth-child(2) a');
    var x2 = document.querySelector('tr:nth-child(2) a');
    alert(x1 + ', ' + x2);
});

It seems to depend on there being a row that doesn't contain an <a>, as you'd find in a header row. Here's a test page:

http://jsfiddle.net/GKb2g/4/

I'll hopefully post back here once I've found the cause, but in the meantime, you're best off using a selectXPath selector.