JSON in JavaScript

The main use of JSON is to fetch JSON data from a web server and convert JSON data to JavaScript object for use in the web page.

JSON Example:

var data = '{ "book" : [' +
    '{ "language":"PHP" , "author":"Rasmus Lerdorf" },' +
    '{ "language":"C" , "author":"Dennis Ritchie" },' +
    '{ "language":"Java" , "author":"James Gosling" } ]}';

We can use JavaScript eval() function to convert a JSON text into a JavaScript object.

var obj = eval ("(" + data + ")");

JSON and JavaScript Example:

Language: <span id="lang0"></span><br>
Author: <span id="auth0"></span><br>

Language: <span id="lang1"></span><br>
Author: <span id="auth1"></span><br>

<script>
var data = '{ "book" : [' +
    '{ "language":"PHP" , "author":"Rasmus Lerdorf" },' +
    '{ "language":"C" , "author":"Dennis Ritchie" },' +
    '{ "language":"Java" , "author":"James Gosling" } ]}';

var obj = eval ("(" + data + ")");

document.getElementById("lang0").innerHTML = obj.book[0].language
document.getElementById("auth0").innerHTML = obj.book[0].author

document.getElementById("lang1").innerHTML = obj.book[1].language
document.getElementById("auth1").innerHTML = obj.book[1].author
</script>

The output of the Program:

Language: PHP

Author: Rasmus Lerdorf

Language: C

Author: Dennis Ritchie

eval() function can be used to execute any JavaScript; this represents a potential security problem.

JSON parser is used to convert JSON text to a JavaScript object, JSON parser only recognize JSON text and the script does not compile.

JSON Parser Example:

obj = JSON.parse(data);

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