CODEWITHSUNDEEP
javascriptscreen-scrapingcasperjs
someone235
someone235

Reputation: 586

Can't get links with CasperJS

I try to run this code and gets "undefined". Does anyone have an idea what is wrong with this code?

var casper = require('casper').create();

casper.start('http://casperjs.org/', function() {
    this.echo(document.querySelector('a'));
});

casper.run();

Upvotes: 0

Views: 123

Answers (2)

ddprrt
ddprrt

Reputation: 7584

You can't access DOM functionality from your Node environment without explicitly stating so. CasperJS has the evaluate function for that:

var casper = require('casper').create();

casper.start('http://casperjs.org/', function() {
    this.echo(this.evaluate(function() {
        //we can now execute DOM functionality
        return document.querySelector('a').toString();
    }));
});

casper.run();

Upvotes: 1

Artjom B.
Artjom B.

Reputation: 61952

CasperJS is built on top of PhantomJS which has two contexts. The inner page context casper.evaluate() is sandboxed and is the only one that has access to the DOM.

DOM nodes cannot be passed to the outside context, so you need to return some representation of the element that you can work with:

this.echo(this.evaluate(function(){
    return document.querySelector('a').href;
}));

I suggest that you look into CasperJS functions that are abstractions from this like getElementInfo() and getElementAttribute().

The PhantomJS documentation says:

Note: The arguments and the return value to the evaluate function must be a simple primitive object. The rule of thumb: if it can be serialized via JSON, then it is fine.

Closures, functions, DOM nodes, etc. will not work!

Upvotes: 1

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