JavaScript Object Notation is a lightweight data-interchange
format. JSON is syntax for storing and exchanging text
information. Much like XML. JSON is
smaller than XML, and faster and easier to parse.
It is easy for machines to parse and generate. It’s based on JavaScript Programming language.
JSON is a text format that is completely language independent but uses
conventions that are familiar to programmers of the C-family of languages,
including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These
properties make JSON an ideal data-interchange language.
JSON Example:-
{ "employees":
[ { "firstName":"John"
, "lastName":"Doe" },
{ "firstName":"Anna" , "lastName":"Smith" },
{ "firstName":"Peter" , "lastName":"Jones" }
]
}
{ "firstName":"Anna" , "lastName":"Smith" },
{ "firstName":"Peter" , "lastName":"Jones" }
]
}
Create Web Page :-
<!DOCTYPE html><html><body>
<h2>JSON Object Creation in JavaScript</h2>
<p> Name: <span id="jname"></span><br
/>
Age: <span id="jage"></span><br />
Address: <span id="jstreet"></span><br />
Phone: <span id="jphone"></span><br /> </p>
<script>
var JSONObject= { "name":"Virendra maurya", "street":"B-403
new ashok nagar", "age":26, "phone":"9555845453"};document.getElementById("jname").innerHTML=JSONObject.name
document.getElementById("jage").innerHTML=JSONObject.age document.getElementById("jstreet").innerHTML=JSONObject.street
document.getElementById("jphone").innerHTML=JSONObject.phone
</script>
</body>
</html>
Why
we use Json:
For
AJAX applications, JSON is faster and easier than XML:
Using
XML
Fetch
an XML document
- Use the XML DOM to loop through the document
- Extract values and store in variables
Using
JSON
- Fetch a JSON string
- eval() the JSON string
Converting a JSON Text to a JavaScript Object
Since JSON syntax is a subset of JavaScript
syntax, the JavaScript function eval() can be used to convert a JSON text into
a JavaScript object.
The eval() function uses the JavaScript compiler which will parse
the JSON text and produce a JavaScript object. The text must be wrapped in
parenthesis to avoid a syntax error:
<script>
var txt = '{ "employees" : [' + '{
"firstName":"Virendra" ,
"lastName":"maurya" },' +
'{ "firstName":"Kuldeep" ,
"lastName":"Singh" },' +
'{ "firstName":"Salmaan" ,
"lastName":"Khan" } ]}'; *//json Object//*
var obj = eval ("(" + txt + ")"); *//convert Json object into Javascript.//*
document.getElementById("fname").innerHTML =
obj.employees[1].firstName
document.getElementById("lname").innerHTML =
obj.employees[1].lastName
</script>
</body>
JSON Parser
he eval() function can
compile and execute any JavaScript. This represents a potential security
problem.It is safer to use a JSON parser to convert a JSON text to a JavaScript
object. A JSON parser will recognize only JSON text and will not compile scripts.In
browsers that provide native JSON support, JSON parsers are also faster.Native
JSON support is included in newer browsers and in the newest ECMAScript
(JavaScript) standard.
