Retrieve server responses in Javascript following a request initiated by Javascript

Question

Retrieve server responses in Javascript following a request initiated by Javascript

Can someone help me with my JavaScript function that sends a request to an aspx page? Here is the code:

 var xhr = ("XMLHttpRequest" in window) ? new XMLHttpRequest() : new ActiveXObject("Msxml3.XMLHTTP");
    xhr.open("GET", 'http://www.example.net/abc.aspx', true);
    xhr.send("");

After sending this request, I need to receive a response from the page and handle it on the client side. Can anyone guide me on how to accomplish this?

javascript request response

Answer 1

Answer №1

To receive the response asynchronously from XMLHttpRequest, you need to set the onreadystatechange property to a callback function in the open() method with the third parameter as true. This callback function will be executed once the response is ready in the browser:

xhr.open("GET", 'http://www.example.net/abc.aspx', true);
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4)  { 
    var serverResponse = xhr.responseText;
  }
};
xhr.send(null);

For further information on this topic, feel free to refer to the following article:

AJAX Patterns: XMLHttpRequest Call

Answer 2

To receive the response asynchronously from XMLHttpRequest, you need to set the onreadystatechange property to a callback function in the open() method with the third parameter as true. This callback function will be executed once the response is ready in the browser:

xhr.open("GET", 'http://www.example.net/abc.aspx', true);
xhr.onreadystatechange = function() {
  if (xhr.readyState === 4)  { 
    var serverResponse = xhr.responseText;
  }
};
xhr.send(null);

For further information on this topic, feel free to refer to the following article:

AJAX Patterns: XMLHttpRequest Call

Answer 3

Answer №2

To ensure cross-browser functionality, a bit more effort is required. However, once accomplished, you will have a reusable function that does not rely on any external library.

// Here is how easy it is to make a call
ajax( "http://www.example.net/abc.aspx", function( data ){
    // Process the server's response here
    alert(data);
});

///////////////////////////////////////////////////////////////////////////////

function getXmlHttpObject() {
    var xmlHttp;
    try {
        // For Firefox, Opera 8.0+, Safari
        xmlHttp = new XMLHttpRequest();
    } catch (e) {
        // For Internet Explorer
        try {
            xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
    }
    if (!xmlHttp) {
        alert("Your browser does not support AJAX!");
    }
    return xmlHttp;
}


function ajax(url, onSuccess, onError) {

    var xmlHttp = getXmlHttpObject();

    xmlHttp.onreadystatechange = function() {
      if (this.readyState === 4) {

            // Execute onSuccess if status is 200 and it is a function
            if (this.status === 200 && typeof onSuccess == 'function') {
                onSuccess(this.responseText);
            }

            // Execute onError if it is a function
            else if(typeof onError == 'function') {
                onError();
            }

        }
    };
    xmlHttp.open("GET", url, true);
    xmlHttp.send(null);
    return xmlHttp;
}

Answer 4

To ensure cross-browser functionality, a bit more effort is required. However, once accomplished, you will have a reusable function that does not rely on any external library.

// Here is how easy it is to make a call
ajax( "http://www.example.net/abc.aspx", function( data ){
    // Process the server's response here
    alert(data);
});

///////////////////////////////////////////////////////////////////////////////

function getXmlHttpObject() {
    var xmlHttp;
    try {
        // For Firefox, Opera 8.0+, Safari
        xmlHttp = new XMLHttpRequest();
    } catch (e) {
        // For Internet Explorer
        try {
            xmlHttp = new ActiveXObject("Msxml2.XMLHTTP");
        } catch (e) {
            xmlHttp = new ActiveXObject("Microsoft.XMLHTTP");
        }
    }
    if (!xmlHttp) {
        alert("Your browser does not support AJAX!");
    }
    return xmlHttp;
}


function ajax(url, onSuccess, onError) {

    var xmlHttp = getXmlHttpObject();

    xmlHttp.onreadystatechange = function() {
      if (this.readyState === 4) {

            // Execute onSuccess if status is 200 and it is a function
            if (this.status === 200 && typeof onSuccess == 'function') {
                onSuccess(this.responseText);
            }

            // Execute onError if it is a function
            else if(typeof onError == 'function') {
                onError();
            }

        }
    };
    xmlHttp.open("GET", url, true);
    xmlHttp.send(null);
    return xmlHttp;
}

Answer 5

Answer №3

To receive the response, you will need to include a readystatechange event handler function. This function will be triggered once the response is available for reading:

xhr.onreadystatechange = function() {
    if (this.readyState !== 4) return; // not ready yet
    if (this.status === 200) { // HTTP 200 OK
        alert(this.responseText);
    } else {
        // handle server errors here
    }
};
xhr.open('GET', 'http://www.example.net/abc.aspx', true);
xhr.send();

Additionally:

("XMLHttpRequest" in window)

While using in is typically a good way to check for property existence, it's not ideal in this case.

The issue arises with IE7+ where, even if the ‘native XMLHttpRequest’ option is disabled, XMLHttpRequest remains as a property in window but with a value of null. In such cases, it's recommended to use a simple truth test for better compatibility and fallback options:

var xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('MSXML2.XMLHttp');

Answer 6

To receive the response, you will need to include a readystatechange event handler function. This function will be triggered once the response is available for reading:

xhr.onreadystatechange = function() {
    if (this.readyState !== 4) return; // not ready yet
    if (this.status === 200) { // HTTP 200 OK
        alert(this.responseText);
    } else {
        // handle server errors here
    }
};
xhr.open('GET', 'http://www.example.net/abc.aspx', true);
xhr.send();

Additionally:

("XMLHttpRequest" in window)

While using in is typically a good way to check for property existence, it's not ideal in this case.

The issue arises with IE7+ where, even if the ‘native XMLHttpRequest’ option is disabled, XMLHttpRequest remains as a property in window but with a value of null. In such cases, it's recommended to use a simple truth test for better compatibility and fallback options:

var xhr = window.XMLHttpRequest ? new XMLHttpRequest() : new ActiveXObject('MSXML2.XMLHttp');

Answer 7

Answer №4

If jQuery is your preference, you can utilize the following code snippet for making ajax calls:

  const requestData = { item1: "Information", item2: "Details"};

  const urlRequest = "http://www.samplewebsite.com/data.php";

  $.ajax({
    type: "POST",
    url: urlRequest,
    data: requestData,
  })
    .done(function (response, status, xhr) {
      // Perform operations
    })
    .fail(function (response, status, xhr) {
      alert("Oops! Unable to connect to server at the moment :(");
    })
    .always(function (response, status, xhr) {});

Answer 8

If jQuery is your preference, you can utilize the following code snippet for making ajax calls:

  const requestData = { item1: "Information", item2: "Details"};

  const urlRequest = "http://www.samplewebsite.com/data.php";

  $.ajax({
    type: "POST",
    url: urlRequest,
    data: requestData,
  })
    .done(function (response, status, xhr) {
      // Perform operations
    })
    .fail(function (response, status, xhr) {
      alert("Oops! Unable to connect to server at the moment :(");
    })
    .always(function (response, status, xhr) {});

Retrieve server responses in Javascript following a request initiated by Javascript

Answer №1

Answer №2

Answer №3

Answer №4

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