I am not sure whether I got the idea of express MVC right:
If I want to make a single page app and dynamically change the HTML, is it something express can help me with? or do I get static pages that if I want to change I have to use front-end JavaScript?
To be more specific, the HTML (or Jade) templates can can change the HTML that is in the front-end somehow?
If I want to make a single page app and dynamically change the HTML,
is it something express can help me with?
Yes.
or do I get static pages that if I want to change I have to use
front-end JavaScript?
Yes, you will need to use JavaScript in the front-end to change the pages if you don't want to refresh the entire page.
To be more specific, the HTML (or Jade) templates can can change
the HTML that is in the front-end somehow?
Typically the HTML (or Jade) templates that you use in Express.js will produce the initial version of the page.
As the user interacts with the page on the browser (say the user clicks on a link or selects something from a dropdown list) your client-side code will submit an Ajax request to the server, Express.js will process this request and return JSON (not HTML) back to the client, and your front-end JavaScript will repopulate some data on the client. Keep in mind that at this point you won't be producing more HTML from the server, though.
Your Express.js could return HTML instead of JSON for these requests but that gets messy pretty quick so most people writing Single Page Apps chose to return JSON back to the client and use client-side JavaScript to repopulate whatever DOM elements need to be updated.
Related
Suppose we have a login page where, in the first stage, we are asked to enter our email. We send this information to the server, which searches whether there is an account with this email, and if there is, our goal is to change the state of the page, to a page where the user is asked to enter the password for this account. If, on the other hand, there is no account with that email, the state of the page changes to one where the user signs up. And let's say that, for the sake of aesthetics, all this happens using the same url.
My question is, what is the correct way to inform the client's page to what stage to go into?
Sending the whole html code is an option, but this seems like it will put too much pressure on the server. Is there a cleaner way, that we can send less information, and still be able to have the same result?
I am new to django and web dev so please explain thoroughly.
For a browser engine submitting a form with email is a new page request and a new rendering of HTML after that. The source of new HTML code is your server with Django, so you should generate a new HTML with a relevant template and send it as a response.
Such user provoked events change a state of your application for a given user session, not a page.
For speed you can use caches for styles, for menus, for HTML snippets (headers and footers).
Also you can make a one-page application, but you must use JavaScript framework for it. Then your JavaScript code executing in client's browser can request concise JSON with necessary information instead of full HTML.
Then your JavaScript framework is responsible for a correct insert new dynamic HTML elements in the current document object model (DOM).
I am trying to have a single GAS project that changes its UI by serving up different HTML pages based on what the user clicks. I cannot figure out how to serve up different HTML from the script, replace the current browser page and retain state. Any help appreciated. Thank you.
I use two options:
Have a main page which has buttons or text areas with onchange set to a function which calls back to the server side and gets new page data, then replace the current page or a portion of the page, with the new page.
Pass parameters in the URL and have the server side doGet() parse the parameters and branch to load a given page based on these values.
I have used a combination of both of these effectively. Basically I have a div which has my "menu" and a div which is the section to be replaced. My menu changes and then data is sent back to the server to get the dynamic body. The HTML is returned and then I replace using innerHTML.
In the same code I offer the ability to pass menu values via the published URL. This allows me to go directly to some values if I so choose as I have a Google Site where we embed the script into pages and the menu selections may be specific to that page. It allows us to use an iFrame to show the web app and go directly to the pertinent interface.
With google.script.run you can run any script on the server from the html page. By communicating with the server you have access to PropertiesService which gives you the capability to store information between pages. Personally I like the HTML Service createHtmlOutput(html) because I can edit the html without having to edit a separate page.
I decided to answer your question here so that I could use the code section.
Question:
I am actually looking to avoid manipulating the HTML and serve up a
completely different HTML file stored in the project. How do I make
the page call the script again and replace itself with the new
content?
We I'm guessing that completely replacing the page is not really what you want because the user will suffer a page refresh. But you could create divs like this:
<style>#R01{display:none;}</style>
<div class="replaceable" id="R01"></div>
If you put all your replaceable content in divs like that then you can request content from the server via calls like this:
google.script.run
.withSuccessHandler(updateConversation)
.withFailureHandler(showStatus)
.getConversation();
and put the new content into the appropriate divs and then change the css with another pair and turn the old content off and the new content on. Thereby avoiding a page refresh. Don't forget to save the old data into the PropertiesService first. So I don't think changing the entire page is the way to go but I could be wrong. I think just changing some of the internal content will avoid the need for a total page refresh. If you want to change images you can avoid another download by using CSS Sprites
I am running a node.js server, and it is rendering a web page wonderfully. When I look at this in a browser, it runs exactly as I expect.
However, what I actually want to do is make the call to fully generate the html page - exactly as it is in the browser - within the node.js code, as a call. Currently, I have tried this:
http.request("http://localhost:8000/").end();
(with a few variants). This does exactly what it says, which is to make the single call to the server for the page - what it doesn't do is actually render the page, pulling in all of the other script files, and running the code on the page.
I have tried exploring express and ejs, and I think I need to use one of these, but I cannot find out how to do this fairly straightforward task. All it needs is to render an html page, but it seems to be a whole lot more complex than it should be.
What output do you want? A string of HTML? Maybe you want PhantomJS the headless browser. You could use it to render the page, then get the rendered DOM as a string of HTML.
Use the Mikeal's Request module to make http requests once you captured the response you then can inspect the html however you like.
To make that easier though you should use cheerio, this will give you a jQuery style api to manipulate the html.
Perhaps you are looking for wkhtmltopdf?
In a nutshell, it will render an entire web page (including images and JavaScript) to a PDF document.
How do you validate (for example using http://validator.w3.org/) a multipage jquery mobile site? For example if I navigate away from index.html the page is only a div without a header or body.
"It depends".
Validation only makes sense in the context of HTML documents, and if you are modifying a document with JavaScript you only have the initial state to validate.
You could use a tool such as Selenium to drive the site and take snapshots of the DOM (serialising it to HTML) when it is in different states, then validate those snapshots. (The markup validation series has an API you can call programatically so you could combine those).
If you are generating fragments of HTML on the server (instead of sending pure, structured data to the client) then you can embed those fragments in HTML skeleton documents and validate those. You should have such documents existing for most views anyway (since you don't want to repeat Gawker's mistake by having a fragile site completely dependant on Ajax).
See also Progressive Enhancement and Unobtrusive JavaScript
Can I refresh a HTML component in JSP? I have two dropdowns. On selection of a value in the first dropdown the values in the dropdown box are to be fetched from the database. Is this possible using JSP?
First, JSP is just a view technology which provides a template to write HTML/CSS/JS in and offers facilities to interact with backend Java code using taglibs (like JSTL) and expression language (those ${} things). JSP runs at the server machine, produces a HTML page and sends it to the client side (if you rightclick page and view source in webbrowser, then you should not see any line of Java/JSP code if it has done its work right). JSP does not run at the client machine and can therefore not be directly used to do partial updates in the HTML page.
To achieve what you want, you need to use JavaScript to fire an asynchronous HTTP request (also known as the Ajax technique) to retrieve the data and manipulate the HTML DOM tree accordingly to add the new elements. Since methods to fire Ajax requests and manipulate the HTML DOM may differ among webbrowsers, I strongly recommend to pick the jQuery JavaScript library to keep it concise and simple without any worries about functioning in different webbrowsers.
I've posted an answer in detail about this before, check solution #3 in this answer.