Retrieve the CSS property value of an element on a webpage using a URL that is from the same origin

Question

Retrieve the CSS property value of an element on a webpage using a URL that is from the same origin

Seeking advice on how to obtain the background color of an element located on a different webpage within the same domain. My current approach involves loading the external page into an iframe, but I believe there must be a more efficient method that someone can guide me towards.

Current Approach

To start, I embed the external page within an iframe:

var $page = $('<iframe/>').attr('src', 'http://mydomain.com/page');

I then add this iframe to my existing page:

$('#iframe-placeholder').append($page);

Finally, I retrieve the CSS property:

$('iframe').load(function(){
  var backgroundColor = $(this).contents().find('#my-element').css('backgroundColor');
});

Limitations of Current Method

It's slow
It's asynchronous
It's not entirely effective as it always returns transparent.

Query

Is there a synchronous way to access the CSS property of the external page? Ideally, I would prefer to avoid loading the entire page into an iframe as it seems excessive. Any insights or recommendations would be greatly appreciated...

jquery html css ajax

Answer 1

Answer №1

Have you attempted to asynchronously load the page content and proceed from there?

var bgColor;
$.ajax({
    type: 'GET',
    url: 'http://mydomain.com/page',
    dataType: 'html',
    success: function(pageData) {
        var page = $(pageData);
        bgColor = page.find('#my-element').css('backgroundColor');
    }
});

Please keep in mind that this code has not been tested.

Answer 2

Have you attempted to asynchronously load the page content and proceed from there?

var bgColor;
$.ajax({
    type: 'GET',
    url: 'http://mydomain.com/page',
    dataType: 'html',
    success: function(pageData) {
        var page = $(pageData);
        bgColor = page.find('#my-element').css('backgroundColor');
    }
});

Please keep in mind that this code has not been tested.

Answer 3

Answer №2

Yes, I understand the allure of using iframes to bypass the same origin policy, but I want to bring your attention to another solution: CORS

Imagine a scenario where the website alice.com holds data that bob.com needs access to. By enabling CORS requests, alice.com can include specific response headers that allow bob.com to retrieve the data.

Step-by-Step Example :

// Initialize the XHR object.
function setupCORSRequest(method, url) {
  var xhr = new XMLHttpRequest();
  if ("withCredentials" in xhr) {
    // XHR for Chrome/Firefox/Opera/Safari.
    xhr.open(method, url, true);
  } else if (typeof XDomainRequest != "undefined") {
    // XDomainRequest for IE.
    xhr = new XDomainRequest();
    xhr.open(method, url);
  } else {
    // CORS not supported.
    xhr = null;
  }
  return xhr;
}

// Utility function to extract the title tag from the response.
function fetchTitle(text) {
  return text.match('<title>(.*)?</title>')[1];
}

// Execute the CORS request.
function initiateCorsRequest() {
  // All HTML5 Rocks properties support CORS.
  var url = 'http://updates.html5rocks.com';

  var xhr = createCORSRequest('GET', url);
  if (!xhr) {
    alert('CORS not supported');
    return;
  }

  // Define response handlers.
  xhr.onload = function() {
    var text = xhr.responseText;
    var title = getTitle(text);
    alert('Response received from CORS request to ' + url + ': ' + title);
  };

  xhr.onerror = function() {
    alert('Oops, an error occurred while making the request.');
  };

  xhr.send();
}

Test out the code and monitor the network requests in your browser's developer tools to observe the actual HTTP request being sent.

For further insight into how this technique operates, feel free to explore the provided website.

Answer 4

Yes, I understand the allure of using iframes to bypass the same origin policy, but I want to bring your attention to another solution: CORS

Imagine a scenario where the website alice.com holds data that bob.com needs access to. By enabling CORS requests, alice.com can include specific response headers that allow bob.com to retrieve the data.

Step-by-Step Example :

// Initialize the XHR object.
function setupCORSRequest(method, url) {
  var xhr = new XMLHttpRequest();
  if ("withCredentials" in xhr) {
    // XHR for Chrome/Firefox/Opera/Safari.
    xhr.open(method, url, true);
  } else if (typeof XDomainRequest != "undefined") {
    // XDomainRequest for IE.
    xhr = new XDomainRequest();
    xhr.open(method, url);
  } else {
    // CORS not supported.
    xhr = null;
  }
  return xhr;
}

// Utility function to extract the title tag from the response.
function fetchTitle(text) {
  return text.match('<title>(.*)?</title>')[1];
}

// Execute the CORS request.
function initiateCorsRequest() {
  // All HTML5 Rocks properties support CORS.
  var url = 'http://updates.html5rocks.com';

  var xhr = createCORSRequest('GET', url);
  if (!xhr) {
    alert('CORS not supported');
    return;
  }

  // Define response handlers.
  xhr.onload = function() {
    var text = xhr.responseText;
    var title = getTitle(text);
    alert('Response received from CORS request to ' + url + ': ' + title);
  };

  xhr.onerror = function() {
    alert('Oops, an error occurred while making the request.');
  };

  xhr.send();
}

Test out the code and monitor the network requests in your browser's developer tools to observe the actual HTTP request being sent.

For further insight into how this technique operates, feel free to explore the provided website.

Retrieve the CSS property value of an element on a webpage using a URL that is from the same origin

Answer №1

Answer №2

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