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JSON – Quick Guide ”; Previous Next JSON – Overview JSON or JavaScript Object Notation is a lightweight text-based open standard designed for human-readable data interchange. Conventions used by JSON are known to programmers, which include C, C++, Java, Python, Perl, etc. JSON stands for JavaScript Object Notation. The format was specified by Douglas Crockford. It was designed for human-readable data interchange. It has been extended from the JavaScript scripting language. The filename extension is .json. JSON Internet Media type is application/json. The Uniform Type Identifier is public.json. Uses of JSON It is used while writing JavaScript based applications that includes browser extensions and websites. JSON format is used for serializing and transmitting structured data over network connection. It is primarily used to transmit data between a server and web applications. Web services and APIs use JSON format to provide public data. It can be used with modern programming languages. Characteristics of JSON JSON is easy to read and write. It is a lightweight text-based interchange format. JSON is language independent. Simple Example in JSON The following example shows how to use JSON to store information related to books based on their topic and edition. { “book”: [ { “id”:”01″, “language”: “Java”, “edition”: “third”, “author”: “Herbert Schildt” }, { “id”:”07″, “language”: “C++”, “edition”: “second”, “author”: “E.Balagurusamy” } ] } After understanding the above program, we will try another example. Let”s save the below code as json.htm − Live Demo <html> <head> <title>JSON example</title> <script language = “javascript” > var object1 = { “language” : “Java”, “author” : “herbert schildt” }; document.write(“<h1>JSON with JavaScript example</h1>”); document.write(“<br>”); document.write(“<h3>Language = ” + object1.language+”</h3>”); document.write(“<h3>Author = ” + object1.author+”</h3>”); var object2 = { “language” : “C++”, “author” : “E-Balagurusamy” }; document.write(“<br>”); document.write(“<h3>Language = ” + object2.language+”</h3>”); document.write(“<h3>Author = ” + object2.author+”</h3>”); document.write(“<hr />”); document.write(object2.language + ” programming language can be studied ” + “from book written by ” + object2.author); document.write(“<hr />”); </script> </head> <body> </body> </html> Now let”s try to open json.htm using IE or any other javascript enabled browser that produces the following result − You can refer to JSON Objects chapter for more information on JSON objects. JSON – Syntax Let”s have a quick look at the basic syntax of JSON. JSON syntax is basically considered as a subset of JavaScript syntax; it includes the following − Data is represented in name/value pairs. Curly braces hold objects and each name is followed by ”:”(colon), the name/value pairs are separated by , (comma). Square brackets hold arrays and values are separated by ,(comma). Below is a simple example − { “book”: [ { “id”: “01”, “language”: “Java”, “edition”: “third”, “author”: “Herbert Schildt” }, { “id”: “07”, “language”: “C++”, “edition”: “second”, “author”: “E.Balagurusamy” } ] } JSON supports the following two data structures − Collection of name/value pairs − This Data Structure is supported by different programming languages. Ordered list of values − It includes array, list, vector or sequence etc. JSON – DataTypes JSON format supports the following data types − Sr.No. Type & Description 1 Number double- precision floating-point format in JavaScript 2 String double-quoted Unicode with backslash escaping 3 Boolean true or false 4 Array an ordered sequence of values 5 Value it can be a string, a number, true or false, null etc 6 Object an unordered collection of key:value pairs 7 Whitespace can be used between any pair of tokens 8 null empty Number It is a double precision floating-point format in JavaScript and it depends on implementation. Octal and hexadecimal formats are not used. No NaN or Infinity is used in Number. The following table shows the number types − Sr.No. Type & Description 1 Integer Digits 1-9, 0 and positive or negative 2 Fraction Fractions like .3, .9 3 Exponent Exponent like e, e+, e-, E, E+, E- Syntax var json-object-name = { string : number_value, …….} Example Example showing Number Datatype, value should not be quoted − var obj = {marks: 97} String It is a sequence of zero or more double quoted Unicode characters with backslash escaping. Character is a single character string i.e. a string with length 1. The table shows various special characters that you can use in strings of a JSON document − Sr.No. Type & Description 1 “ double quotation 2 backslash 3 / forward slash 4 b backspace 5 f form feed 6 n new line 7 r carriage return 8 t horizontal tab 9 u four hexadecimal digits Syntax var json-object-name = { string : “string value”, …….} Example Example showing String Datatype − var obj = {name: ”Amit”} Boolean It includes true or false values. Syntax var json-object-name = { string : true/false, …….} Example var obj = {name: ”Amit”, marks: 97, distinction: true} Array It is an ordered collection of values. These are enclosed in square brackets which means that array begins with .[. and ends with .].. The values are separated by , (comma). Array indexing can be started at 0 or 1. Arrays should be used when the key names are sequential integers. Syntax [ value, …….] Example Example showing array containing multiple objects − { “books”: [ { “language”:”Java” , “edition”:”second” }, { “language”:”C++” , “lastName”:”fifth” }, { “language”:”C” , “lastName”:”third” } ] } Object It is an unordered set of name/value pairs. Objects are enclosed in curly braces that is, it starts with ”{” and ends with ”}”. Each name is followed by ”:”(colon) and the key/value pairs are separated by , (comma). The keys must be strings and should be different from each other. Objects should be used when the key names are arbitrary strings. Syntax { string : value, …….} Example Example showing Object − { “id”: “011A”, “language”: “JAVA”, “price”: 500, } Whitespace It can be inserted between any pair of tokens. It can be added to make a code more readable. Example shows declaration with and without whitespace − Syntax {string:” “,….} Example var obj1 = {“name”: “Sachin Tendulkar”} var obj2 = {“name”: “SauravGanguly”}