title: Scrape web with x-ray
body: <p>I'm using x-ray to extract some data from a web site but when I get to the point to crawl to another page using the built-in functionality, it simply doesn't work.</p>
  
  <p><strong>UnitPrice</strong> is the parameter I want to extract but I get "<em>undefined</em>" all the time. </p>
  
  <p>As you can see, I'm passing the href value previously extracted on the url property.</p>
  
  <pre><code>var Xray = require('x-ray');
  var x = Xray();
  var x = Xray({
    filters: {
      cleanPrice: function (value) {
        return typeof value === 'string' ? value.replace(/\r|\t|\n|€/g, "").trim() : value
      },
      whiteSpaces: function (value) {
        return typeof value === 'string' ? value.replace(/ +/g, ' ').trim() : value
      }
    }
  });
  
  x('https://www.simply.es/compra-online/aceite-vinagre-y-sal.html',
    '#content &gt; ul',
    [{
      name: '.descripcionProducto | whiteSpaces',
      categoryId: 'input[name="idCategoria"]@value',
      productId: 'input[name="idProducto"]@value',
      url: 'li a@href',
      price: 'span | cleanPrice',
      image: '.miniaturaProducto@src',
      unitPrice: x('li a@href', '.precioKilo')
    }])
    .paginate('.link@href')
    .limit(1)
    // .delay(500, 1000)
    // .throttle(2, 1000)
    .write('results.json')
  </code></pre>