JSON

JSON :  JavaScript Object Notation.
JSON is a syntax for storing and exchanging data.
JSON is text, written with JavaScript object notation. 

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

In JSON, values must be one of the following data types:

• a string
• a number
• an object
• an array
• a boolean
• null

In JavaScript values can be all of the above, plus any other valid JavaScript expression, including

• a function
• a date
• undeifined

JSON.parse()

• A common use of JSON is to exchange data to/from a web server.
• When receiving data from a web server, the data is always a string.
• Parse the data with JSON.parse(), and the data becomes a JavaScript object.

Example :

<script>

var xmlhttp = new XMLHttpRequest();

xmlhttp.onreadystatechange = function() {

  if (this.readyState == 4 && this.status == 200) {

    var myObj = JSON.parse(this.responseText);

    document.getElementById("demo").innerHTML = myObj.name;

  }

};

xmlhttp.open("GET", "json_demo.txt", true);

xmlhttp.send();

</script>

JSON.stringify()

• A common use of JSON is to exchange data to/from a web server.
• When sending data to a web server, the data has to be a string.
• Convert a JavaScript object into a string with JSON.stringify().

Example :

var obj = { name: "John", age: 30, city: "New York" };
var myJSON = JSON.stringify(obj);
document.getElementById("demo").innerHTML = myJSON;