Javascript initial data strategy - javascript

In order to keep my page clean i have created a few javascript files that are combined at production mode into fewer files.
I am using a data- attribute in body to determine which script to run.The problem is that when i need some initial data.In this case i use a script tag and put there a json array with my data.
These data may change so i am wondering whether it is better to make a json request for the data and not put them in my page directly ?

Related

Create HTML dynamically depending of Node variables

I am using Node.js with Express as a server. The user can upload a .CSV file with data. I'm parsing these data and store this in a main array composed of arrays (each line = one array). For now, I'm rendering a page (made with Pug) with this variable.
res.render('index', { rows });
The page is rendering as I would like to the user. However, I'd like to save the rendered "index" in a HTML file. The goal is to convert the HTML file into a PDF (which already works as a result of previous tests with static HTML).
Is it possible to save the rendered page as a HTML file? I'd like to take advantage of the feature of passing variable through the render function.
Another solution would be to generate by myself the HTML file, and do my own logic inside the Node.js route. That seems a long and useless solution since the render function do it well. I just need to save it instead of rendering it.
You could call PUG directly to trigger a render and then save the produced file (https://pugjs.org/)

Is it good to return html code to jquery?

I'm working on a project where it has a number of pages. Each page displays 10 rows where the layout that is using for each page is different. Until now I had the html code of each row in a javascript code and based on the page's url I was using the appropriate html code (if statement). The if statement is inside into a loop which is looping based on the number of rows. The results of the rows are coming from an ajax method. Now I want somehow to separate it so it can be more easily for me to maintain it, basically to remove the html code from the javascript and keep each row's html code into a different file.
Note: the Ajax is in a given time, is sending automatically requests to the php file for any new rows.
One solution which I came out is that I can use the php to create a variable with the html code .
Second solution is to create an array of each record with the html code and then pass it to jquery to print it.
Both solutions I don't know if are good solutions and can help me to maintain the project in the future.
You might consider a template library such as handlebars to help with templating. Frameworks such as AngularJS and Ember also excel at solving these kinds of problems.
Your Web Services API should be returning JSON though, not HTML fragments. Let the client build the DOM, and let the server focus on data.
You should return structured data (see JSON for example) to your AJAX request. This way, you can support multiple interfaces (e.g., a website, an application): each interface will get only the data, and will handle the rendering as it needs.
In your example, you ask for data via an AJAX request, your server responds with a JSON-structured response. JQuery reads it and converts it to javascript array thanks to jQuery.getJSON. With your array, you loop through each element and insert html elements into the webpage.
You have two options:
If your HTML templates is not changing frequently, the best way is to define html templates in your HTML structure using some java script template library (eg. Handlebars) and fill it with data from your AJAX (JSON) requests.
If your HTML templates change frequently or depends on some conditions (data) in row, you should create PHP partial views which generate proper html structure already filled with data.
For many rows it is better idea to create whole table server side to reduce requests.

AngularJS: Render HTML output to a string

I am writing an app that must generate a PDF file based on the HTML generated by AngularJS. I do not want to display this output to the user. I want to capture the rendered HTML to a string and send it to a server, where a service there will receive the HTML source and create the PDF file.
I understand that one way to grab rendered HTML is through accessing the element's innerHTML property after compiling it in a directive. But how can I be certain that there are no further digests that need to take place? Also, can this method work without writing the results to the DOM? -- Or, at least, without displaying the results to the user? Thanks!

Generating HTML in JavaScript vs loading HTML file

Currently I am creating a website which is completely JS driven. I don't use any HTML pages at all (except index page). Every query returns JSON and then I generate HTML inside JavaScript and insert into the DOM. Are there any disadvantages of doing this instead of creating HTML file with layout structure, then loading this file into the DOM and changing elements with new data from JSON?
EDIT:
All of my pages are loaded with AJAX calls. But I have a structure like this:
<nav></nav>
<div id="content"></div>
<footer></footer>
Basically, I never change nav or footer elements, they are only loaded once, when loading index.html file. Then on every page click I send an AJAX call to the server, it returns data in JSON and I generate HTML code with jQuery and insert like this $('#content').html(content);
Creating separate HTML files, and then for example using $('#someID').html(newContent) to change every element with JSON data, will use even more code and I will need 1 more request to server to load this file, so I thought I could just generate it in browser.
EDIT2:
SEO is not very important, because my website requires logging in so I will create all meta tags in index.html file.
In general, it's a nice way of doing things. I assume that you're updating the page with AJAX each time (although you didn't say that).
There are some things to look out for. If you always have the same URL, then your users can't come back to the same page. And they can't send links to their friends. To deal with this, you can use history.pushState() to update the URL without reloading the page.
Also, if you're sending more than one request per page and you don't have an HTML structure waiting for them, you may get them back in a different order each time. It's not a problem, just something to be aware of.
Returning HTML from the AJAX is a bad idea. It means that when you want to change the layout of the page, you need to edit all of your files. If you're returning JSON, it's much easier to make changes in one place.
One thing that definitly matters :
How long will it take you to develop a new system that will send data as JSON + code the JS required to inject it as HTML into the page ?
How long will it take to just return HTML ? And how long if you can re-use some of your already existing server-side code ?
and check how much is the server side interrection of your pages...
also some advantages of creating pure HTML :
1) It's simple markup, and often just as compact or actually more compact than JSON.
2) It's less error prone cause all you're getting is markup, and no code.
3) It will be faster to program in most cases cause you won't have to write code separately for the client end.
4) The HTML is the content, the JavaScript is the behavior. You're mixing both for absolutely no compelling reason.
in javascript or nay other scripting language .. if you encountered a problem in between the rest of the code will not work
and also it is easier to debug in pure html pages
my opinion ... use scriptiong code wherever necessary .. rest of the code you can do in html ...
it will save the triptime of going to server then fetch the data and then displaying it again.
Keep point No. 4 in your mind while coding.
I think that you can consider 3 methods:
Sending only JSON to the client and rendering according to a template (i.e.
handlerbar.js)
Creating the pages from the server-side, usually faster rendering also you can cache the page.
Or a mixture of this would be to generate partial views from the server and sending them to the client, for example it's like having a handlebar template on the client and applying the data from the JSON, but only having the same template on the server-side and rendering it on the server and sending it to the client in the final format, on the client you can just replace the partial views.
Also some things to think about determined by the use case of the applicaton, is that if you are targeting SEO you should consider ColBeseder advice, of if you are targeting mobile users, probably you would better go with the JSON only response, as this is a more lightweight response.
EDIT:
According to what you said you are creating a single page application, if this is correct, then probably you can go with either the JSON or a partial views like AngularJS has. But if your server-side logic is written to handle only JSON response, then probably you could better use a template engine on the client like handlerbar.js, underscore, or jquery templates, and you can define reusable portions of your HTML and apply to it the data from the JSON.
If you cared about SEO you'd want the HTML there at page load, which is closer to your second strategy than your first.
Update May 2014: Google claims to be getting better at executing Javascript: http://googlewebmastercentral.blogspot.com/2014/05/understanding-web-pages-better.html Still unclear what works and what does not.
Further updates probably belong here: Do Google or other search engines execute JavaScript?

Passing parameter map (list of values) to JQuery

to initialize a javascript loaded grid, I need to pass a list of values from controller/gsp. Since the javascript is activated once the page is rendered/loaded, there may not be a direct way to do it. 2 possibilities
1. do an ajax call, and retrieve the list of values from the server
2. store the list in html as a hidden element, and read it from javascript.
option 2 seems better as it avoids few calls back to server. So, which control should I use for a list of values? Any jQuery code snippet to read it back into array/list.
thanks in advance.
It depends on the size of that data. It it's small enough, you could embed it in the page. For example, to populate a calendar with events, I used something like:
<div id="calendar" data-events="[/* event list */]"></div>(the data-events attribute contained a JavaScript array of event objects in JSON format)
However, if you're talking about a huge amount of data, loading it (possibly in chunks) asynchronously after the page load (or when the document is ready) could increase your app's performace and make it more interactive (i.e. I don't want to wait and load that data if the next thing I'm gonna do is navigate away)
Does that answer your question?
You can directly write JavaScript from the server side. I don't know about grails, but here's a very simple example in php:
<script type="text/javascript">
var someVar = "<?php echo $someServerVar;?>";
</script>
Sure, this example is very simple, but you get the idea. And most languages will have some sort of function that escapes JavaScript strings (basically turn " into \" and new lines into \n).
If you put a script like that at the top of your <head>, then those variables will be accessible from all other scripts on the page.

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