Chrome Developer Console is console.loging this:
Your JSON sent is>> {yourVariable: "nothing yet"}
So i know the value "nothing yet" in the {yourVariable: "nothing yet"} JSON object is a string. But how do I know the type of the key yourVariable?
Is there a way how to find that out using the Chrome console only?
All object keys are strings with quotes or without quotes. Try this way to see it. May be you are confused with console print because console print it without quotes and we usually write with quotes.
var jsonObj = {person:"me","age":"30", 123:"123"};
Object.keys(jsonObj).forEach(function(key){
console.log(typeof key)}
);
I have a slightly different take on this question which does not invalidate the comments or answer that you received, but is worth considering.
Because you are talking about JSON, there is no intrinsic datatype in your example. As stated on the JSON.org page:
JSON (JavaScript Object Notation) is a lightweight data-interchange
format. It is easy for humans to read and write. It is easy for
machines to parse and generate.
The point is, that there is a difference between JSON, which is a representation of javascript objects, arrays etc., and variables of those types in javascript.
If you remind yourself that JSON is a form of serialization it makes a lot more sense. Javascript objects for example, can include functions, but a javascript function is not a portable thing, so in rendering some JSON from a javascript object, it is up to the language creating the JSON to do whatever it it needs to in order to convert the data it needs to represent, and that may include simplification and in many cases removal of elements that are incompatible JSON.
The other thing to keep in mind, is that all modern languages have functions or libraries that can parse JSON and turn them into variables or objects that work in those languages. In doing so, they have arguments that can completely change the way the JSON is converted back into instance variables.
For example, in PHP you can choose to have the JSON create one or more PHP objects, or an array of php variables.
In summary, JSON doesn't have variables with datatypes at all. It is a representation of data, that is portable across languages, but the languages must decode the JSON and create objects or variables that are valid in their own runtime.
I see advantages of getting JSON response and formatting in client side but are there any advantages by using JSON for form submission compared to normal submission?
One thing comes to mind when dealing with POST data is useless repetition:
For example, in POST we have this:
partners[]=Apple&partners[]=Microsoft&partners[]=Activision
We can actually see, that there is a lot of repetition here, where as when we are sending JSON:
{"partners":["Apple","Microsoft","Activision"]}
59 characters versus 47. In this small sample it looks miniscule, but these savings could go up and up, and even several bytes will save you some data. Of course, there is the parsing of data on server side, which could even out the differences, but still, i saw this sometimes helping when dealing with slower connections (looking at you, 3G and EDGE).
I didn't see any mention of file submission so I thought I'd chime in. FormData seems to be the standard way of submitting files to a server over AJAX. I didn't come across any solutions using JSON but there might be a way to serialize/deserialize files ...
It probably depends on your server side application. You are usually posting data to servers using POST, so how do you format underline data depends on how do you want for your server to process it. POST provides some form of key->value protocol, while in JSON you can put more than that. You can also transfer json using GET by placing it in url.
You must look on json as a way how data is written, while normal submission with POST should give you just a way how you transport data(of course you can abuse key->value feature of it for ordering your data).
There exists protocols on top of HTTP, that could help you define interface to your web application. One good example is RESTfull http://en.wikipedia.org/wiki/Representational_state_transfer
Specifically for submitting forms, I don't see any advanatages, POST was designed for this in a first place. There are cases where you want to transmit not only data from form, but also some metadata in this case json might help you by encoding form data(with metadata) in some json format, but at the end you will be still abusing POST for transferig this json data.
Hope I answered your question.
I don't see any apparent advantages for basic form submission. But when it comes to handling complex structures you'll start to realize the advantage of organizing your data.
So if you have a simple contact form (name, email, message) stick with normal form POSTing. But think about submitting a complete user's CV for example, it's very annoying to handle the massive amount of variables in your server-side script.
Here's an example for using JSON with PHP
//Here are the submission data
{
"personalInformation": {
"name": "hey",
"age": "20"
},
"education": {
"entry1": {
"type": "Collage",
"year": "2012"
},
"entry2": {
"type": "Highschool",
"year": "2010"
}
}
}
$CV_Data = json_decode($_POST['json_form'], true);
$CV_Data['personalInformation']['name'];
$CV_Data['personalInformation']['age'];
//Or you can loop
foreach($CV_Data['education'] as $entry){
$entry['type'];
$entry['year'];
}
As you can see, using JSON here makes it a lot easier for you to work on your data.
I am actually wrestling with the same problem. My use case requires that a potentially complex tree to be posted to the server. Some framework are able to decode two dimensional arrays as form attributes (Spring WebMVC is one I know of). Even so, this only helps you in the specific case when you are sending a nested array. The inherent nature of name-value-pair makes it unsuitable for transmitting a tree more than one level deep. In the past, I have used hacks like sending URL-encoded JSON as attribute value:
val0=%7B%22name%22%3A%22value%22%7D&val1=something&val2=something+else
However, this approach gets messy and difficult to debug when the object becomes more complex. In addition, many frameworks provide tools that automagically map JSON form post to objects (e.g.: Jackson for Java), it seems obtuse not to take advantage of these tools.
So ultimately, the choice rests on the complexity of the object you are sending. If the object is limited to one level deep, use straight name-value-pair; if the object is complex and involves a deeply-nested tree, use JSON.
I've looked on Wikipedia and Googled it and read the official documentation, but I still haven't got to the point where I really understand what JSON is, and why I'd use it.
I have been building applications using PHP, MySQL and JavaScript / HTML for a while, and if JSON can do something to make my life easier or my code better or my user interface better, then I'd like to know about it. Can someone give me a succinct explanation?
JSON (JavaScript Object Notation) is a lightweight format that is used for data interchanging. It is based on a subset of JavaScript language (the way objects are built in JavaScript). As stated in the MDN, some JavaScript is not JSON, and some JSON is not JavaScript.
An example of where this is used is web services responses. In the 'old' days, web services used XML as their primary data format for transmitting back data, but since JSON appeared (The JSON format is specified in RFC 4627 by Douglas Crockford), it has been the preferred format because it is much more lightweight
You can find a lot more info on the official JSON web site.
JSON is built on two structures:
A collection of name/value pairs. In various languages, this is realized as an object, record, struct, dictionary, hash table, keyed list, or associative array.
An ordered list of values. In most languages, this is realized as an array, vector, list, or sequence.
JSON Structure
Here is an example of JSON data:
{
"firstName": "John",
"lastName": "Smith",
"address": {
"streetAddress": "21 2nd Street",
"city": "New York",
"state": "NY",
"postalCode": 10021
},
"phoneNumbers": [
"212 555-1234",
"646 555-4567"
]
}
JSON in JavaScript
JSON (in Javascript) is a string!
People often assume all Javascript objects are JSON and that JSON is a Javascript object. This is incorrect.
In Javascript var x = {x:y} is not JSON, this is a Javascript object. The two are not the same thing. The JSON equivalent (represented in the Javascript language) would be var x = '{"x":"y"}'. x is an object of type string not an object in its own right. To turn this into a fully fledged Javascript object you must first parse it, var x = JSON.parse('{"x":"y"}');, x is now an object but this is not JSON anymore.
See Javascript object Vs JSON
When working with JSON and JavaScript, you may be tempted to use the eval function to evaluate the result returned in the callback, but this is not suggested since there are two characters (U+2028 & U+2029) valid in JSON but not in JavaScript (read more of this here).
Therefore, one must always try to use Crockford's script that checks for a valid JSON before evaluating it. Link to the script explanation is found here and here is a direct link to the js file. Every major browser nowadays has its own implementation for this.
Example on how to use the JSON parser (with the json from the above code snippet):
//The callback function that will be executed once data is received from the server
var callback = function (result) {
var johnny = JSON.parse(result);
//Now, the variable 'johnny' is an object that contains all of the properties
//from the above code snippet (the json example)
alert(johnny.firstName + ' ' + johnny.lastName); //Will alert 'John Smith'
};
The JSON parser also offers another very useful method, stringify. This method accepts a JavaScript object as a parameter, and outputs back a string with JSON format. This is useful for when you want to send data back to the server:
var anObject = {name: "Andreas", surname : "Grech", age : 20};
var jsonFormat = JSON.stringify(anObject);
//The above method will output this: {"name":"Andreas","surname":"Grech","age":20}
The above two methods (parse and stringify) also take a second parameter, which is a function that will be called for every key and value at every level of the final result, and each value will be replaced by result of your inputted function. (More on this here)
Btw, for all of you out there who think JSON is just for JavaScript, check out this post that explains and confirms otherwise.
References
JSON.org
Wikipedia
Json in 3 minutes (Thanks mson)
Using JSON with Yahoo! Web Services (Thanks gljivar)
JSON to CSV Converter
Alternative JSON to CSV Converter
JSON Lint (JSON validator)
The Concept Explained - No Code or Technical Jargon
What is JSON? – How I explained it to my wifeTM
Me: “It’s basically a way of communicating with someone in writing....but with very specific rules.
Wife: yeah....?
Me: In prosaic English, the rules are pretty loose: just like with cage fighting. Not so with JSON. There are many ways of describing something:
• Example 1: Our family has 4 people: You, me and 2 kids.
• Example 2: Our family: you, me, kid1 and kid2.
• Example 3: Family: [ you, me, kid1, kid2]
• Example 4: we got 4 people in our family: mum, dad, kid1 and kid2.
Wife: Why don’t they just use plain English instead?
Me: They would, but remember we’re dealing with computers. A computer is stupid and is not going to be able to understand sentences. So we gotta be really specific when computers are involved otherwise they get confused. Furthermore, JSON is a fairly efficient way of communicating, so most of the irrelevant stuff is cut out, which is pretty hand. If you wanted to communicate our family, to a computer, one way you could do so is like this:
{
"Family": ["Me", "Wife", "Kid1", "Kid2"]
}
……and that is basically JSON. But remember, you MUST obey the JSON grammar rules. If you break those rules, then a computer simply will not understand (i.e. parse) what you are writing.
Wife: So how do I write in Json?
A good way would be to use a json serialiser - which is a library which does the heavy lifting for you.
Summary
JSON is basically a way of communicating data to someone, with very, very specific rules. Using Key Value Pairs and Arrays. This is the concept explained, at this point it is worth reading the specific rules above.
In short - JSON is a way of serializing in such a way, that it becomes JavaScript code. When executed (with eval or otherwise), this code creates and returns a JavaScript object which contains the data you serialized. This is available because JavaScript allows the following syntax:
var MyArray = [ 1, 2, 3, 4]; // MyArray is now an array with 4 elements
var MyObject = {
'StringProperty' : 'Value',
'IntProperty' : 12,
'ArrayProperty' : [ 1, 2, 3],
'ObjectProperty' : { 'SubObjectProperty': 'SomeValue' }
}; // MyObject is now an object with property values set.
You can use this for several purposes. For one, it's a comfortable way to pass data from your server backend to your JavaScript code. Thus, this is often used in AJAX.
You can also use it as a standalone serialization mechanism, which is simpler and takes up less space than XML. Many libraries exists that allow you to serialize and deserialize objects in JSON for various programming languages.
In short, it is a scripting notation for passing data about. In some ways an alternative to XML, natively supporting basic data types, arrays and associative arrays (name-value pairs, called Objects because that is what they represent).
The syntax is that used in JavaScript and JSON itself stands for "JavaScript Object Notation". However it has become portable and is used in other languages too.
A useful link for detail is here:
http://secretgeek.net/json_3mins.asp
The JSON format is often used for serializing and transmitting structured data over a network connection. It is used primarily to transmit data between a server and web application, serving as an alternative to XML.
JSON is JavaScript Object Notation. It is a much-more compact way of transmitting sets of data across network connections as compared to XML.
I suggest JSON be used in any AJAX-like applications where XML would otherwise be the "recommended" option. The verbosity of XML will add to download time and increased bandwidth consumption ($$$). You can accomplish the same effect with JSON and its mark-up is almost exclusively dedicated to the data itself and not the underlying structure.
the common short answer is: if you are using AJAX to make data requests, you can easily send and return objects as JSON strings. Available extensions for Javascript support toJSON() calls on all javascript types for sending data to the server in an AJAX request. AJAX responses can return objects as JSON strings which can be converted into Javascript objects by a simple eval call, e.g. if the AJAX function someAjaxFunctionCallReturningJson returned
"{ \"FirstName\" : \"Fred\", \"LastName\" : \"Flintstone\" }"
you could write in Javascript
var obj = eval("(" + someAjaxFunctionCallReturningJson().value + ")");
alert(obj.FirstName);
alert(obj.LastName);
JSON can also be used for web service payloads et al, but it is really convenient for AJAX results.
Update (ten years later): Don't do this, use JSON.parse
I like JSON mainly because it's so terse. For web content that can be gzipped, this isn't necessarily a big deal (hence why xhtml is so popular). But there are occasions where this can be beneficial.
For example, for one project I was transmitting information that needed to be serialized and transmitted via XMPP. Since most servers will limit the amount of data you can transmit in a single message, I found it helpful to use JSON over the obvious alternative, XML.
As an added bonus, if you're familiar with Python or Javascript, you already pretty much know JSON and can interpret it without much training at all.
What is JSON?
JavaScript Object Notation (JSON) is a lightweight data-interchange format inspired by the object literals of JavaScript.
JSON values can consist of:
objects (collections of name-value pairs)
arrays (ordered lists of values)
strings (in double quotes)
numbers
true, false, or null
JSON is language independent.
JSON with PHP?
After PHP Version 5.2.0, JSON extension is decodes and encodes functionalities as default.
Json_encode - returns the JSON representation of values
Json_decode - Decodes the JSON String
Json_last_error - Returns the last error occured.
JSON Syntax and Rules?
JSON syntax is derived from JavaScript object notation syntax:
Data is in name/value pairs
Data is separated by commas
Curly braces hold objects
Square brackets hold arrays
Sometimes technicality is given where none is required, and while many of the top voted answers are accurately technical and specific, I personally don't think they are any more easy to understand, or succinct, as what can be found on Wikipedia, or in official documentation.
The way I like to think of JSON is exactly what it is - a language within a world of different languages. However, the difference between JSON and other languages is that "everyone" "speaks" JSON, along with their "native language."
Using a real world example, let's pretend we have three people. One person speaks Igbo as their native tongue. The second person would like to interact with the first person, however, the first person speaks Yoruba as their first language.
What can we do?
Thankfully, the third person in our example grew up speaking English, but also happens to speak both Igbo and Yoruba as second languages, and so can act as an intermediary between the first two individuals.
In the programming world, the first "person" is Python, the second "person" is Ruby, and the third "person" is JSON, who just so happens to be able to "translate" Ruby into Python and vice versa! Now obviously this analogy isn't a perfect one, but, as someone who is bilingual, I believe it's an easy way to look at how JSON interacts with other programming languages.
We have to do a project on college and we faced a very big problem, it is called Same Origin Policy. Amog other things, it makes that your XMLHttpRequest method from Javascript can't make requests to domains other than the domain that your site is on.
For example you can't make request to www.otherexample.com if your site is on www.example.com. JSONRequest allows that, but you will get result in JSON format if that site allows that(for example it has a web service that returns messages in JSON).
That is one problem where you could use JSON perhaps.
Here is something practical: Yahoo JSON
The difference between JSON and conventional syntax would be as follows (in Javascript)
Conventional
function Employee(name, Id, Phone, email){
this.name = name;
this.Id = Id;
this.Phone = Phone;
this.email = email;
}
//access or call it as
var Emp = new Employee("mike","123","9373849784","mike.Anderson#office.com");
With JSON
if we use JSON we can define in different way as
function Employee(args){
this.name = args.name;
this.Id = args.Id;
this.Phone = args.Phone;
this.email = args.email;
}
//now access this as...
var Emp = new Employee({'name':'Mike', 'Id':'123', 'Phone':'23792747', 'email':'mike.adnersone#office.com'});
The important thing we have to remember is that, if we have to build the "Employee" class or modal with 100 elements without JSON method we have to parse everything when creating class. But with JSON we can define the objects inline only when a new object for the class is defined.
so this line below is the way of doing things with JSON(just a simple way to define things)
var Emp = new Employee({'name':'Mike', 'Id':'123', 'Phone':'23792747', 'email':'mike.adnersone#office.com'});
It's very simple. JSON stands for Java Script Object Notation. Think of it as an alternative to using XML for transferring data between software components.
For example, I recently wrote a bunch of web services that returned JSON, and some Javascript developers then wrote code which called the services and consumed the information returned in that format.
JSON(Javascript object notation) is a light weight data format for data exchange/transfer. Its in key value pair as the JavaScript is.
For REST API its widely used for data transfer from server to client. Nowadays many of the social media sites are using this. Although I don't see this as robust as XML with respect of data types. XML has very rich datatypes and XSD. JSON is bit lacking in this.
For same amount of string data JSON will be lighter compare to XML as XML has all that opening and closing tags, etc...
In the Java context, one reason why JSON might want to be used, is that it provides a very good alternative to Java's Serialization framework, which has been shown (historically) to be subject to some fairly serious vulnerabilities.
Joshua Bloch discusses this in depth in Item 85 "Prefer Alternatives to Java Serialization" (Effective Java 3rd Edition)
Java's Serialization was initially meant to translate data structures into a format that could be easily transmitted or stored. JSON meets this requirement, without the serious exploits referred to above.
Try the following code to parse your php json response:
read.php
<script
src="https://code.jquery.com/jquery-3.2.1.min.js"
integrity="sha256-hwg4gsxgFZhOsEEamdOYGBf13FyQuiTwlAQgxVSNgt4="
crossorigin="anonymous"></script>
<script type="text/javascript">
$.ajax({
url:'index.php',
data:{},
type:"POST",
success:function(result) {
jsondecoded = $.parseJSON(result);
$.each(jsondecoded, function(index, value) {
$("#servers").text($("#servers").text() + " " + value.servername);
console.log(value.start);
console.log(value.end);
console.log(value.id);
});
},
statusCode: {
404: function() {
alert( "page not found" );
}
}
});
</script>
server.php
<?php
echo '[{"start":"2017-08-29","end":"2017-09-01","id":"22"},{"start":"2017-09-03","end":"2017-09-06","id":"23"}]';
?>