Recently I've been working with leaflets, and I'm currently looking at several plugins.
Several of the plugins I've seen (including Leaflet.markercluster) use json to plot points, but instead of using the actual stream, or a json file, the programmer includes a javascript .js file where a variable is set with the json stream. So the js file with the json data looks like this:
var data = [
{"loc":[41.575330,13.102411], "title":"aquamarine"},
{"loc":[41.575730,13.002411], "title":"black"},
{"loc":[41.807149,13.162994], "title":"blue"},
{"loc":[41.507149,13.172994], "title":"chocolate"}
]
I've been working with other type of javascript charts, and most of them read and process a json stream.
It seems these plugins will not work if I create a service that returns json.
Why not use json instead of including a js file that sets a variable with a json stream?
I'm not a javascript expert, but I find it easier to generate json than a javascript file with json in it.
You are wrong about concepts.
1st. JavaScript as a language has its own syntax, so, if you have a function that receive a JSON object as a parameter and you pass it a Number or a String, it'll will throw an Error when you try to access some property. For Ex.
function myjson (obj) {
console.log(obj.prop)
}
myjson(34); //wrong
myjson("{prop: 123}") //wrong
myjson({prop: 123}) //Good, will print 123
Now, imagine that you have some scripts, many .js files that you have indexed in your HTML file, like
<script src="/mycode.js"> </script>
<script src="/myapp.js"> </script>
And you want to add some data, like the one you show for the plot points; then you have to include it in two ways, putting that in a .js file or getting it from a service with an AJAX call.
If you add that in a .js file, you'll have access to them directly from your code, like this
var data = [
{"loc":[41.575330,13.102411], "title":"aquamarine"},
{"loc":[41.575730,13.002411], "title":"black"},
{"loc":[41.807149,13.162994], "title":"blue"},
{"loc":[41.507149,13.172994], "title":"chocolate"}
]
console.log(data)
and if you put that in a .json file file this
/mydata.json
[
{"loc":[41.575330,13.102411], "title":"aquamarine"},
{"loc":[41.575730,13.002411], "title":"black"},
{"loc":[41.807149,13.162994], "title":"blue"},
{"loc":[41.507149,13.172994], "title":"chocolate"}
]
you'll have to fetch and parse the data yourself
fetch("/mydata.json").then(async data => {
var myjson = await data.text();
myjson = JSON.parse(myjson);
console.log(myjson) //A Javascript object
console.log(myjson[1]) //The first element
})
I like #FernandoCarvajal's answer, but I would add more context to it:
JSON is more recent than JS (you could see JSON as a "spin-off" of JS, even though it is now used in combination with much more languages than just JS).
Before JSON was widespread, the main and easiest way to load external data in Browsers was the technique you saw in the plugins demo: assign data into a global variable, which you can use in the next script. Browsers happily execute JS even from cross domain (unless you explicitly specify a Content Security Policy). The only drawback is that you have to agree on a global variable name beforehand. But for static sites (like GitHub pages in the case of the plugins demo you mention), it is easy for the developer(s) to agree on such a convention.
At this stage, you should understand that using this simple technique already fits the job for the sake of the plugins static demo. It also avoids browsers compatibility issues, aligning with Leaflet wide browsers compatibility.
With the advent of richer clients / Front-End, typically with AJAX, we can get rid of the global variable name agreement issue, but now we may face cross domain difficulty, as pointed out by #Barmar's comment. We also start hitting browsers compatibility hell.
Now that we can load arbitrary data without having to agree on a static name beforehand, we can leverage Back-End served dynamic content to a bigger scale.
To workaround the cross domain issue, and before CORS was widespread, we started using JSONP: the Front-End specifies the agreed (callback) name in its request. But in fact we just fallback to a similar technique as in point 2, mainly adding asynchronicity.
Now that we have CORS, we can more simply use AJAX / fetch techniques, and avoid security issues inherent to JSONP. We also replace the old school XML by the more JS-like JSON.
There is nothing preventing you from replacing the old school technique in point 2 by a more modern JSON consumption. If you want to ensure wide browsers compatibility, make sure to use libraries that take care of it (like jQuery, etc.). And if you need cross domain, make sure to enable CORS.
I'm trying to use the Planetside 2 database to create a simple application for educational purposes. However, I'm stuck. I need to convert an XML file to a Javascript object so i can use the data easily and display it on my app. Problem is, the file is a link, i suppose. I tried it just like you would with a file located on the same server/PC however that doesnt work.
This is the link:
http://census.daybreakgames.com/xml/get/ps2:v2/character/?name.first_lower=litebrite
My question is, How do i convert/turn this onto an object usable in Javascript? (I have absolute no experience in javascript, hence the reason i'm not using the JSON verion of the file)
Thanks
I am using C# to create a rather complicated data object that contains a couple of lists of objects that is then serialized and sent to the client. I like this approach a lot because I am using the same object definition in both my client and server side code.
I'd like to create some sort of reference file for Visual Studio 2012 so that intellisense can help me out, typos in my javascript code seem to be my biggest problem in debugging.
Does anybody have any tips for doing this? I understand that as I add new properties to the C# class I will need to refresh this reference file.
You can use T4 template to generate javascipt viewmodel file from your C# class.
Take a look at this article.
Also some more information available.
I have been using a DOMParser object to parse a text string to an XML tree. However it is not available in the context of a Web Worker (and neither is, of course, document.ELEMENT_NODE or the various other constants that would be needed). Is there any other way to do that?
Please note that I do not want to manipulate the DOM of the current page. The XML file won't contain HTML elements or anything of the sort. In fact, I do not want to touch the document object at all. I simply want to provide a text string like the following:
<car color="blue"><driver/></car>
...and get back a suitable tree structure and a way to traverse it. I also do not care about schema validation or anything fancy. I know about XML for <SCRIPT>, which many may find useful (hence I'm linking to it here), however its licensing is not really suitable for me. I'm not sure if jQuery includes an XML parser (I'm fairly new to this stuff), but even if it does (and it is usable inside a Worker), I would not include an extra ~50K lines of code just for this function.
I suppose I could write a simple XML parser in JavaScript, I'm just wondering if I'm missing a quicker option.
according to the spec
The DOM APIs (Node objects, Document objects, etc) are not available to workers in this version of this specification.
I guess thats why DOMParser is not availlable, but I don't really understand why that decision was made. (fetching and processing an XML document in a WebWorker does not seems unreasonnable)
but you can import other tools available: a "Cross Platform XML Parsing in JavaScript"
At this point I like to share my parser: https://github.com/tobiasnickel/tXml
with its tXml() method you can parse a string into an object and it takes only 0.5kb minified + gzipped
I would like to read a pptx file in javascript, so I would like to unzip it and read the content in memory. I don't want to store the file first on a server. I want to choose a file with a input type file and just use the file of the input-element and read it binary or something like that.
I found a lot of libraries to unzip zip-files from url, I tried to look at the code but I couldn't figure it out to use it for a blob or byte array.
I can read some stuff like the things described here: http://en.wikipedia.org/wiki/ZIP_%28file_format%29#File_headers
But I don't know how deflating works on byte- or bit-level.
(You've said you want to use an input element, so I'm guessing this is browser-based JavaScript.)
Your first step will be to use the File API to read the file as a binary string. See my answer to this other question for an example of that. Then you'll need to find a library. A quick search discovered this one that implements both inflate and deflate. (I don't have personal experience using it, just found it in an answer to this other question.)
Naturally this will only work on quite modern browsers that support the File API. Otherwise, you have no option but to push the file to a server and do the work there, since you can't access the content of the file in the browser without the File API.