JavaScript Execution

Executing script on loaded document

Arguments

Examples

A. Execute JavaScript function

SELECT * 
FROM http://www.delven.io/test/execute.html
EVENTFLOW
{
  "execute" : ["window.scrollTo(0, 0)", "document.write('Hello World')"]
}

A. Execute JavaScript on [DOMElement] (https://developer.mozilla.org/en-US/docs/Web/API/Element)

Before a funtion can be executed a DOMElement first need to be located

SELECT css("#btn") 
FROM http://www.delven.io/test/execute.html 
EVENTFLOW
[
  {
    "by-css"    : "#btn",
    "execute" :  ["$.click()"]
  }
]

Full JavaScript support : ECMAScript 6

Delven allows for low lever interaction with documents via JavaScript(ECMAScript 6+) scripts. The native keyword is applied to a script to indicate that the script is implemented in native code.

Context Object

Name Spec Data Types Description
args Object of Key:Value Parameters passed to the function
session Object of Key:Value Contains information about current extract session
document DOMDocument Currently loaded document
config Object of Key:Value Request configuration

Native method can return three different types of results.

  • Simple value
  • JSON Object
  • Object Array

NULL values will throw an exception.

Examples

Calling native function

Following example will call page-interceptor.js afer page have been loaded and execute product intercept function. Calling native functions takes a special $ prefix such as $product

SELECT $product() AS product
FROM http://www.delven.io/test/execute.html 
NATIVE "page-interceptor.js"

Passing arguments to function

Arguments passed to the function take an JSON object and can be accessed from the context object via context.args.

SELECT $product({"field":"product"}) AS product
FROM http://www.delven.io/test/execute.html 
NATIVE "page-interceptor.js"

Script to execute : page-interceptor.js

export function product(context) 
{
    var arg = context.args;
    var $   = context.jQuery;
  
    var result =
    {
        name: $('.productName h1').text().trim(),
        price: $('.price .value').text().trim(),
        description: $('.description[itemprop="description"]').text().trim()
    };

    return result;
}

Page Interceptors : intercept.js

There are cases when we want to capture and manipulate requests/responses before they get processed by the interpetter.

Interceptors allow you to:

  • Intercept a request by implementing the request function: This method is called before reguest is send to the backend.

  • Intercept a response by implementing the response function: This method is called right after interpretter receives the response from the backend, so you can modify the response and make other actions.

  var interceptor = 
  {
      request: function(context) 
      {
          var document = context.document;   
          var config   = context.config;             
          config.headers['x-session-token'] = 'secret-token';            
      },

      response : function(context) 
      {
          var document = context.document;   
          document.title = 'Intercepted Document'          
      }
  };

 // Register our interceptor
 $psql.config.addInterceptor(interceptor);

Adding dependencies : require