What are the endless possibilities of JavaScript?

Question

What are the endless possibilities of JavaScript?

My main goal is to maximize client-side functionality using JavaScript. Specifically, I want to create an interface that displays information to users and processes their responses using JavaScript. I plan to use a web server only for retrieving a data file and sending back a modified version of it. I am curious if the following tasks are achievable with JavaScript:

Is it possible for JavaScript to extract content from an external web page? Essentially, can JavaScript on my local machine read the contents of a specified web page?
Can JavaScript handle input values submitted through an HTML form? For example, can JavaScript process data filled out by a user in an HTML form created using HTML and JavaScript without sending the data to a web server?
After processing data locally, I intend for JavaScript to create a local data file and then send it to a PHP server. Is this feasible with JavaScript?
Lastly, can JavaScript trigger the execution of a local Python program from within the script?

I welcome any feedback or insights on these questions.

javascript ajax webforms client-side

Answer 1

Answer №1

While it is technically possible, in reality, accessing external content is restricted by the same origin policy. This limitation applies to both reading and writing external content. One workaround is loading an iframe with a different domain's page, but programmatic access is still not allowed. Some solutions exist for Internet Explorer based on Andy E's answer.
Accessing GET arguments from a HTML form submission using Javascript is feasible but limited due to size restrictions (around 1024 bytes). It's recommended to keep all functionalities within one page for better performance.
To enable users to download files locally, tools like Downloadify can be used. Generating and uploading files to a server require user interaction, while sending generated data as POST data is possible without issues.
Executing local files directly from a webpage is a challenging task due to browser security measures. Installing extensions or utilizing proprietary scripting languages like WScript and VBScript may provide some solutions, though full execution of local files even in Internet Explorer seems unlikely nowadays.

Answer 2

While it is technically possible, in reality, accessing external content is restricted by the same origin policy. This limitation applies to both reading and writing external content. One workaround is loading an iframe with a different domain's page, but programmatic access is still not allowed. Some solutions exist for Internet Explorer based on Andy E's answer.
Accessing GET arguments from a HTML form submission using Javascript is feasible but limited due to size restrictions (around 1024 bytes). It's recommended to keep all functionalities within one page for better performance.
To enable users to download files locally, tools like Downloadify can be used. Generating and uploading files to a server require user interaction, while sending generated data as POST data is possible without issues.
Executing local files directly from a webpage is a challenging task due to browser security measures. Installing extensions or utilizing proprietary scripting languages like WScript and VBScript may provide some solutions, though full execution of local files even in Internet Explorer seems unlikely nowadays.

Answer 3

Answer №2

When using Internet Explorer to access local files, there are some workarounds that can help you achieve your goals:

Although the same origin policy limits pages in IE, you can bypass this restriction using the WinHttpRequest COM interface.
GET requests can be managed with window.location.search, but POST request variables remain inaccessible as Pekka pointed out.
The COM interface for FileSystemObject allows you to read and write local text files.
Using the WScript.Shell interface's Exec method, you can execute a local program.

Most of what you need is possible through Internet Explorer, though running the COM interfaces will require permission (usually indicated by the yellow alert bar). Alternatively, consider creating a Windows Desktop Gadget or an HTML Application (HTA) on Vista or Windows 7.

If all else fails, transform your computer into a functioning server using XAMPP and develop your pages in PHP.

Answer 4

When using Internet Explorer to access local files, there are some workarounds that can help you achieve your goals:

Although the same origin policy limits pages in IE, you can bypass this restriction using the WinHttpRequest COM interface.
GET requests can be managed with window.location.search, but POST request variables remain inaccessible as Pekka pointed out.
The COM interface for FileSystemObject allows you to read and write local text files.
Using the WScript.Shell interface's Exec method, you can execute a local program.

Most of what you need is possible through Internet Explorer, though running the COM interfaces will require permission (usually indicated by the yellow alert bar). Alternatively, consider creating a Windows Desktop Gadget or an HTML Application (HTA) on Vista or Windows 7.

If all else fails, transform your computer into a functioning server using XAMPP and develop your pages in PHP.

Answer 5

Answer №3

It seems I have the solution you are looking for. Here is the best course of action:

Select a JavaScript library such as jQuery, Dojo, or YUI. Personally, I recommend using jQuery as it can help reduce the load on your system.
Instead of storing form data in a local file, store them in local variables. Process the data and then send it to the server (for further processing like updating a database) using an XMLHttp request. Once the webservice returns the data, process it and update the DOM accordingly.

Here is a sample demonstration:

--This Represents the DOM:

Name: <input type='text' id='name' />

<a href='javascript:void(0)' onClick='submit()'>Submit Form</a><br>
<div id='target'></div>

--This Portrays the JavaScript Code:
function submit()
{
var _name=$('#name').val(); // Collect text box data
// Validate the data or perform any other desired actions

callWebservice(_name,_suc,_err);
}

function _suc(data)
{
// Data successfully returned from the server
$('#target').html(data);
}

function _err()
{
// Handle errors that occur on the server
}

// In reality, JSON is commonly used for most tasks. This showcases the basic concept of manipulating the DOM with JavaScript, calling services, and avoiding page reloads to display new data to viewers.

Answer 6

It seems I have the solution you are looking for. Here is the best course of action:

Select a JavaScript library such as jQuery, Dojo, or YUI. Personally, I recommend using jQuery as it can help reduce the load on your system.
Instead of storing form data in a local file, store them in local variables. Process the data and then send it to the server (for further processing like updating a database) using an XMLHttp request. Once the webservice returns the data, process it and update the DOM accordingly.

Here is a sample demonstration:

--This Represents the DOM:

Name: <input type='text' id='name' />

<a href='javascript:void(0)' onClick='submit()'>Submit Form</a><br>
<div id='target'></div>

--This Portrays the JavaScript Code:
function submit()
{
var _name=$('#name').val(); // Collect text box data
// Validate the data or perform any other desired actions

callWebservice(_name,_suc,_err);
}

function _suc(data)
{
// Data successfully returned from the server
$('#target').html(data);
}

function _err()
{
// Handle errors that occur on the server
}

// In reality, JSON is commonly used for most tasks. This showcases the basic concept of manipulating the DOM with JavaScript, calling services, and avoiding page reloads to display new data to viewers.

Answer 7

Answer №4

There are numerous possibilities when it comes to what you can accomplish, but remember that consistency is key. Even if you mention in response to the original poster that you want to develop a group game, my advice remains focused on ensuring that whatever you implement on the client side is thoroughly verified on the server side. It's vital to always keep in mind the principle of Never Trust the Client!

I have no desire to repeat tasks unnecessarily.

If you opt for client-side actions, be prepared to address them both on the client and server sides or risk encountering widespread cheating.

Answer 8

There are numerous possibilities when it comes to what you can accomplish, but remember that consistency is key. Even if you mention in response to the original poster that you want to develop a group game, my advice remains focused on ensuring that whatever you implement on the client side is thoroughly verified on the server side. It's vital to always keep in mind the principle of Never Trust the Client!

I have no desire to repeat tasks unnecessarily.

If you opt for client-side actions, be prepared to address them both on the client and server sides or risk encountering widespread cheating.

Answer 9

Answer №5

When we first embarked on our project, we were faced with the same question.
Ultimately, we made the decision to shift most of the workload to the JavaScript side. Here's how we structured our setup:

On the backend, we exclusively send and receive JSON data.
We opted for Erlang, although Python would have worked just as well. The backend is responsible for managing authentication/security and storage.

As for the frontend, we utilized HTML+CSS for visual elements and JavaScript for logic.
To convert the JSON data into HTML, we implemented a JS template engine. While we developed our own called PURE, there are numerous others available. While MVC might be excessive for the client-side, in my opinion, using a template engine provides the bare minimum for code separation.

The speed of response is exceptional. Once the page along with the JS/CSS is loaded (whether fresh or cached), only the data needs to traverse the network for each request.

Answer 10

When we first embarked on our project, we were faced with the same question.
Ultimately, we made the decision to shift most of the workload to the JavaScript side. Here's how we structured our setup:

On the backend, we exclusively send and receive JSON data.
We opted for Erlang, although Python would have worked just as well. The backend is responsible for managing authentication/security and storage.

As for the frontend, we utilized HTML+CSS for visual elements and JavaScript for logic.
To convert the JSON data into HTML, we implemented a JS template engine. While we developed our own called PURE, there are numerous others available. While MVC might be excessive for the client-side, in my opinion, using a template engine provides the bare minimum for code separation.

The speed of response is exceptional. Once the page along with the JS/CSS is loaded (whether fresh or cached), only the data needs to traverse the network for each request.

What are the endless possibilities of JavaScript?

Answer №1

Answer №2

Answer №3

Here is a sample demonstration:

Answer №4

Answer №5

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