Json

JSON JavaScript Object Notation Developed by: Musavir Iftikhar Jan 2007

Introduction A lightweight data-interchange format. Easy for humans to read and write. Alternative solution of XML A text format that is completely language independent Uses convention like C and Java It is JavaScript based Language

JSON values 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.

Data types in JavaScript Primitive data types are as followings Undefined Null Boolean Number and String . <script> int a = 5; Alert (typeof a) // will show int </script>

Built-in Objects in JavaScript Built-in JavaScript objects Image, array and object Following is an instance of image built-in javascript object <script> var Image1 = new Image(); Image1.src = “bird. gif "; </script>

New Object in JavaScript A function in JavaScript is an Object <script> function myFunc(){ } var myObject = new myFunc(); alert(typeof myObject); // displays "object“ </script>

Constructor of object A constructor is the default value of function <script> function myFunc(){ return 5; } var myObject = myFunc(); alert(typeof myObject); // displays "number“ </script>

Object function more Function with default value <script> function myFunc(){ this.StringValue = "This is a String"; } var myObject = new myFunc(); var myObject2 = new myFunc(); alert(myObject2.StringValue); // displays "This is a String“ </script>

Passing values to Objects Function that takes Object’s value <script> function myFunc(StringValue){ this.StringValue = StringValue; } var myObject = new myFunc("This is myObject's string"); var myObject2 = new myFunc("This is a String"); alert(myObject.StringValue); // displays "This is myObject's string" alert(myObject2.StringValue); // displays "This is a String“ </script>

Object with methods A Object with functions is a function that uses other functions for its functionality. <script> function Circle(radius){ this.radius = radius; this.getArea = getArea; this.getCircumference = getCircumference; } function getArea(){ return (this.radius*this.radius*3.14); } function getCircumference(){ var diameter = this.radius*2; var circumference = diameter*3.14; return circumference; }

Code.. continue var bigCircle = new Circle(100); var smallCircle = new Circle(2); alert(bigCircle.getArea()); // displays 31400 alert(bigCircle.getCircumference()); // displays 618 alert(smallCircle.getArea()); // displays 12.56 alert(smallCircle.getCircumference()); // displays 12.56 </script> Note: this key world always point to the variable of that object that is instantiated. The functions that Object using refer to the variable of Object function when they Come across this keyword as this.radius means the radius of the Object function Circle.

Inner or Nested functions Inner Function is created inside the function for Objected Oriented programming style. It is clear and easy to write. Note: the constructor function argument variable must be accessed by using key world this <script> function Circle(radius){ this.radius = radius; this.getArea = function(){ return (this.radius*this.radius*3.14); } this.getCircumference = function(){ var diameter = this.radius*2; var circumference = diameter*3.14; return circumference; } }

Code…continue var bigCircle = new Circle(100); var smallCircle = new Circle(2); alert(bigCircle.getArea()); // displays 31400 alert(smallCircle.getCircumference()); // displays 12.56 </script>

JSON Object object {} { members } members pair pair , members pair string : value array [] [ elements ] elements value value , elements

JSON Object value string number object array true false null string "" " chars " chars char char chars

JSON Object char any-Unicode-character- except- " -or- \ -or- control-character \" \\ \/ \b \f \n \r \t \u four-hex-digits number int int frac int exp int frac exp

JSON Object int digit digit1-9 digits - digit - digit1-9 digits frac . digits exp e digits digits digit digit digits e e e+ e- E E+ E-

Using JSON JSON is available for two sides Server side JSON Format is written in the server specific language as C, C++, C#, java, PHP etc. It is used to decode the client request Client side JSON JavaScript is used to encode the JSON response to convert it into text representation of receiving Object

Server side Requirements Need JSON file written in support server side language as for PHP JSON.php Include into page and create a new instance <?php require_once "JSON.php"; //create a new instance of Services_JSON $json = new Services_JSON(); ?>

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