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Using co

co is a flow library allowing for non-blocking code. With Nightmare, you can use it to yield call chains. The following example searches for github nightmare at Yahoo and returns the first HREF in the search results:

var Nightmare = require('nightmare'),
  co = require('co'),
  nightmare = Nightmare({
    show: true
  });

var run = function*() {
  //declare the result and wait for Nightmare's queue defined by the following chain of actions to complete
  var result = yield nightmare
    //load a url
    .goto('http://yahoo.com')
    //simulate typing into an element identified by a CSS selector
    //here, Nightmare is typing into the search bar
    .type('input[title="Search"]', 'github nightmare')
    //click an element identified by a CSS selector
    //in this case, click the search button
    .click('#uh-search-button')
    //wait for an element identified by a CSS selector
    //in this case, the body of the results
    .wait('#main')
    //execute javascript on the page
    //here, the function is getting the HREF of the first search result
    .evaluate(function() {
      return document.querySelector('#main .searchCenterMiddle li a')
        .href;
    });


  //queue and end the Nightmare instance along with the Electron instance it wraps
  yield nightmare.end();

  //return the HREF
  return result;
};

//use `co` to execute the generator function
co(run)
  .then(function(result) {
    console.log(result);
  }, function(err) {
    console.log(err);
  });

Nightmare internally (partially) implements promises by exposing .then(). This allows it to be yieldable for use under co.

Parameters

Parameters in co are passed by using co.wrap(). The following example is the same as above, with the selector for the link href passed in. This also shows how to pass parameters from the parent Nightmare process to the child Electron process through .evaluate():

var Nightmare = require('nightmare'),
  co = require('co'),
  nightmare = Nightmare({
    show: true
  });

//the generator accepts the selector to get the first search result
var run = function * (selector) {
  //declare the result and wait for Nightmare's queue defined by the following chain of actions to complete
  var result = yield nightmare
    //load a url
    .goto('http://yahoo.com')
    //simulate typing into an element identified by a CSS selector
    //here, Nightmare is typing into the search bar
    .type('input[title="Search"]', 'github nightmare')
    //click an element identified by a CSS selector
    //in this case, click the search button
    .click('#uh-search-button')
    //wait for an element identified by a CSS selector
    //in this case, the body of the results
    .wait('#main')
    //execute javascript on the page
    //here, the function is getting the HREF of the first match do the selector parameter
    //note the selector is passed in as the second argument to evaluate
    .evaluate(function(selector) {
      return document.querySelector(selector)
        .href;
    }, selector);

  //queue and end the Nightmare instance along with the Electron instance it wraps
  yield nightmare.end();

  //return the HREF
  return result;
};

//use `co.wrap()` to execute the generator function, allowing parameters to be passed to the generator
co.wrap(run)('#main .searchCenterMiddle li a')
  .then(function(result) {
    console.log(result);
  }, function(err) {
    console.log(err);
  });

References