Creating Message in JSON with JavaScript("toJSONString()" )

Posted by imomins on July 11, 2011 at 7:12 AM

Creating Message in JSON with JavaScript      

In previous section you have studied about the JSONin JavaScript's some basic concepts of creating a simple object and creating anarray of objects. Now we are going to discuss how to create a message with JSONin JavaScript.

In this example of creating message in JSON withJavaScript we have included "json2.js" file first. After thiswe have created an object variable students which contains two array objects .Again we have created an array object and pushed one array data into it. Messageis then created by converting array object to string by using the function "toJSONString()". Here is the example code of CreatingMessage.htm :

CreatingMessage.htm

<html>

<head>

<title>

Creating Message using JSON in JavaScript

</title>

<script language="javascript" src="json2.js"></script>

<script language="javascript" >

 

  var students = { "Maths" : [ 

  { "Name"  : "Amit",    // First element

  "Marks" : 67,

  "age" : 23 },  

  {

  "Name"  : "Sandeep",  // Second element

  "Marks" : 65,

  "age" : 21 }

 ], 

  "Science" : [ 

   { "Name" : "Shaili",  // First Element

 "Marks"  : 56,

 "age"  : 27 }, 

  { "Name"   : "Santosh", // Second Element

 "Marks"  : 78,

 "age"  : 41 }

  ] 

  } 

  // Printing array elements values 

var i=0

var arrayObject = new Array();

for(i=0;i<students.Maths.length;i++)

{  

  arrayObject.push(students.Maths[i].Name);

  arrayObject.push(students.Maths[i].Marks);

  arrayObject.push(students.Maths[i].age);

}  

  alert("Welcome to JSON Message Example ");

  alert(arrayObject.toJSONString());

</script>

</head>

<body>

 Message creation using JSON in JavaScript

</body>

</html>

To run this example you need to include the JavaScriptfile "json2.js" so that the functions defined for convertingobjects to string and parse them can be done. This can be downloaded from http://www.json.org/json2.js

Here is the "json2.js" file code:

/*

json.js

2008-05-25

Public Domain

No warranty expressed or implied. Use at your own risk.

This file has been superceded by http://www.JSON.org/json2.js

See http://www.JSON.org/js.html

This file adds these methods to JavaScript:

array.toJSONString(whitelist)

boolean.toJSONString()

date.toJSONString()

number.toJSONString()

object.toJSONString(whitelist)

string.toJSONString()

These methods produce a JSON text from a JavaScript value.

It must not contain any cyclical references. Illegal values

will be excluded.

The default conversion for dates is to an ISO string. You can

add a toJSONString method to any date object to get a different

representation.

The object and array methods can take an optional whitelist

argument. A whitelist is an array of strings. If it is provided,

keys in objects not found in the whitelist are excluded.

string.parseJSON(filter)

This method parses a JSON text to produce an object or

array. It can throw a SyntaxError exception.

The optional filter parameter is a function which can filter and

transform the results. It receives each of the keys and values, and

its return value is used instead of the original value. If it

returns what it received, then structure is not modified. If it

returns undefined then the member is deleted.

Example:

// Parse the text. If a key contains the string 'date' then

// convert the value to a date.

myData = text.parseJSON(function (key, value) {

return key.indexOf('date') >= 0 ? new Date(value) : value;

});

This file will break programs with improper for..in loops. See

http://yuiblog.com/blog/2006/09/26/for-in-intrigue/

This file creates a global JSON object containing two methods: stringify

and parse.

JSON.stringify(value, replacer, space)

value any JavaScript value, usually an object or array.

replacer an optional parameter that determines how object

values are stringified for objects without a toJSON

method. It can be a function or an array.

space an optional parameter that specifies the indentation

of nested structures. If it is omitted, the text will

be packed without extra whitespace. If it is a number,

it will specify the number of spaces to indent at each

level. If it is a string (such as '\t' or '&nbsp;'),

it contains the characters used to indent at each level.

This method produces a JSON text from a JavaScript value.

When an object value is found, if the object contains a toJSON

method, its toJSON method will be called and the result will be

stringified. A toJSON method does not serialize: it returns the

value represented by the name/value pair that should be serialized,

or undefined if nothing should be serialized. The toJSON method

will be passed the key associated with the value, and this will be

bound to the object holding the key.

  For example, this would serialize Dates as ISO strings.

   Date.prototype.toJSON = function (key) {

   function f(n) {

   // Format integers to have at least two digits.

   return n < 10 ? '0' + n : n;

 }

   return this.getUTCFullYear() + '-' +

  f(this.getUTCMonth() + 1) + '-' +

  f(this.getUTCDate()) + 'T' +

  f(this.getUTCHours()) + ':' +

  f(this.getUTCMinutes()) + ':' +

  f(this.getUTCSeconds()) + 'Z';

};

You can provide an optional replacer method. It will be passed the

key and value of each member, with this bound to the containing

object. The value that is returned from your method will be

serialized. If your method returns undefined, then the member will

be excluded from the serialization.

If the replacer parameter is an array, then it will be used to

select the members to be serialized. It filters the results such

that only members with keys listed in the replacer array are

stringified.

Values that do not have JSON representations, such as undefined or

functions, will not be serialized. Such values in objects will be

dropped; in arrays they will be replaced with null. You can use

a replacer function to replace those with JSON values.

JSON.stringify(undefined) returns undefined.

The optional space parameter produces a stringification of the

value that is filled with line breaks and indentation to make it

easier to read.

If the space parameter is a non-empty string, then that string will

be used for indentation. If the space parameter is a number, then

the indentation will be that many spaces.

Example:

text = JSON.stringify(['e', {pluribus: 'unum'}]);

// text is '["e",{"pluribus":"unum"}]'

text = JSON.stringify(['e', {pluribus: 'unum'}], null, '\t');

// text is '[\n\t"e",\n\t{\n\t\t"pluribus": "unum"\n\t}\n]'

text = JSON.stringify([new Date()], function (key, value) {

return this[key] instanceof Date ?

'Date(' + this[key] + ')' : value;

});

// text is '["Date(---current time---)"]'

JSON.parse(text, reviver)

This method parses a JSON text to produce an object or array.

It can throw a SyntaxError exception.

The optional reviver parameter is a function that can filter and

transform the results. It receives each of the keys and values,

and its return value is used instead of the original value.

If it returns what it received, then the structure is not modified.

If it returns undefined then the member is deleted.

Example:

// Parse the text. Values that look like ISO date strings will

// be converted to Date objects.

myData = JSON.parse(text, function (key, value) {

var a;

if (typeof value === 'string') {

a =

/^(\d{4})-(\d{2})-(\d{2})T(\d{2}):(\d{2}):(\d{2}(?:\.\d*)?)Z$/.exec(value);

if (a) {

return new Date(Date.UTC(+a[1], +a[2] - 1, +a[3], +a[4],

+a[5], +a[6]));

}

}

return value;

});

myData = JSON.parse('["Date(09/09/2001)"]', function (key, value) {

var d;

if (typeof value === 'string' &&

value.slice(0, 5) === 'Date(' &&

value.slice(-1) === ')') {

d = new Date(value.slice(5, -1));

if (d) {

return d;

}

}

return value;

});

It is expected that these methods will formally become part of the

JavaScript Programming Language in the Fourth Edition of the

ECMAScript standard in 2008.

This is a reference implementation. You are free to copy, modify, or

redistribute.

This code should be minified before deployment.

See http://javascript.crockford.com/jsmin.html

USE YOUR OWN COPY. IT IS EXTREMELY UNWISE TO LOAD CODE FROM SERVERS YOU

DO NOT CONTROL.

*/

/*jslint evil: true */

/*global JSON */

/*members "", "\b", "\t", "\n", "\f", "\r", "\"", JSON, "\\", call,

charCodeAt, getUTCDate, getUTCFullYear, getUTCHours, getUTCMinutes,

getUTCMonth, getUTCSeconds, hasOwnProperty, join, lastIndex, length,

parse, parseJSON, propertyIsEnumerable, prototype, push, replace, slice,

stringify, test, toJSON, toJSONString, toString

*/

if (!this.JSON) {

// Create a JSON object only if one does not already exist. We create the

// object in a closure to avoid global variables.

JSON = function () {

function f(n) {

// Format integers to have at least two digits.

return n < 10 ? '0' + n : n;

}

Date.prototype.toJSON = function (key) {

return this.getUTCFullYear() + '-' +

f(this.getUTCMonth() + 1) + '-' +

f(this.getUTCDate()) + 'T' +

f(this.getUTCHours()) + ':' +

f(this.getUTCMinutes()) + ':' +

f(this.getUTCSeconds()) + 'Z';

};

var cx = /[\u0000\u00ad\u0600-\u0604\u070f\u17b4\u17b5

\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,

escapeable = /[\\\"\x00-\x1f\x7f-\x9f\u00ad\u0600-\u0604\u070f\u17b4\u17b5

\u200c-\u200f\u2028-\u202f\u2060-\u206f\ufeff\ufff0-\uffff]/g,

gap,

indent,

meta = { // table of character substitutions

'\b': '\\b',

'\t': '\\t',

'\n': '\\n',

'\f': '\\f',

'\r': '\\r',

'"' : '\\"',

'\\': '\\\\'

},

rep;

function quote(string) {

// If the string contains no control characters, no quote characters, and no

// backslash characters, then we can safely slap some quotes around it.

// Otherwise we must also replace the offending characters with safe escape

// sequences.

escapeable.lastIndex = 0;

return escapeable.test(string) ?

'"' + string.replace(escapeable, function (a) {

var c = meta[a];

if (typeof c === 'string') {

return c;

}

return '\\u' + ('0000' +

(+(a.charCodeAt(0))).toString(16)).slice(-4);

}) + '"' :

'"' + string + '"';

}

function str(key, holder) {

// Produce a string from holder[key].

var i, // The loop counter.

k, // The member key.

v, // The member value.

length,

mind = gap,

partial,

value = holder[key];

// If the value has a toJSON method, call it to obtain a replacement value.

if (value && typeof value === 'object' &&

typeof value.toJSON === 'function') {

value = value.toJSON(key);

}

// If we were called with a replacer function, then call the replacer to

// obtain a replacement value.

if (typeof rep === 'function') {

value = rep.call(holder, key, value);

}

// What happens next depends on the value's type.

switch (typeof value) {

case 'string':

return quote(value);

case 'number':

// JSON numbers must be finite. Encode non-finite numbers as null.

return isFinite(value) ? String(value) : 'null';

case 'boolean':

case 'null':

// If the value is a boolean or null, convert it to a string. Note:

// typeof null does not produce 'null'. The case is included here in

// the remote chance that this gets fixed someday.

return String(value);

// If the type is 'object', we might be dealing with an object or an array or

// null.

case 'object':

// Due to a specification blunder in ECMAScript, typeof null is 'object',

// so watch out for that case.

if (!value) {

return 'null';

}

// Make an array to hold the partial results of stringifying this object value.

gap += indent;

partial = [];

// If the object has a dontEnum length property, we'll treat it as an array.

if (typeof value.length === 'number' &&

!(value.propertyIsEnumerable('length'))) {

// The object is an array. Stringify every element. Use null as a placeholder

// for non-JSON values.

length = value.length;

for (i = 0; i < length; i += 1) {

partial[i] = str(i, value) || 'null';

}

// Join all of the elements together, separated with commas, and wrap them in

// brackets.

v = partial.length === 0 ? '[]' :

gap ? '[\n' + gap +

partial.join(',\n' + gap) + '\n' +

mind + ']' :

'[' + partial.join(',') + ']';

gap = mind;

return v;

}

// If the replacer is an array, use it to select the members to be stringified.

if (rep && typeof rep === 'object') {

length = rep.length;

for (i = 0; i < length; i += 1) {

k = rep[i];

if (typeof k === 'string') {

v = str(k, value, rep);

if (v) {

partial.push(quote(k) + (gap ? ': ' : ':') + v);

}

}

}

} else {

// Otherwise, iterate through all of the keys in the object.

for (k in value) {

if (Object.hasOwnProperty.call(value, k)) {

v = str(k, value, rep);

if (v) {

partial.push(quote(k) + (gap ? ': ' : ':') + v);

}

}

}

}

// Join all of the member texts together, separated with commas,

// and wrap them in braces.

v = partial.length === 0 ? '{}' :

gap ? '{\n' + gap +

partial.join(',\n' + gap) + '\n' +

mind + '}' :

'{' + partial.join(',') + '}';

gap = mind;

return v;

}

}

// Return the JSON object containing the stringify and parse methods.

return {

stringify: function (value, replacer, space) {

// The stringify method takes a value and an optional replacer, and an optional

// space parameter, and returns a JSON text. The replacer can be a function

// that can replace values, or an array of strings that will select the keys.

// A default replacer method can be provided. Use of the space parameter can

// produce text that is more easily readable.

var i;

gap = '';

indent = '';

// If the space parameter is a number, make an indent string containing that

// many spaces.

if (typeof space === 'number') {

for (i = 0; i < space; i += 1) {

indent += ' ';

}

// If the space parameter is a string, it will be used as the indent string.

} else if (typeof space === 'string') {

indent = space;

}

// If there is a replacer, it must be a function or an array.

// Otherwise, throw an error.

rep = replacer;

if (replacer && typeof replacer !== 'function' &&

(typeof replacer !== 'object' ||

typeof replacer.length !== 'number')) {

throw new Error('JSON.stringify');

}

// Make a fake root object containing our value under the key of ''.

// Return the result of stringifying the value.

return str('', {'': value});

},

parse: function (text, reviver) {

// The parse method takes a text and an optional reviver function, and returns

// a JavaScript value if the text is a valid JSON text.

var j;

function walk(holder, key) {

// The walk method is used to recursively walk the resulting structure so

// that modifications can be made.

var k, v, value = holder[key];

if (value && typeof value === 'object') {

for (k in value) {

if (Object.hasOwnProperty.call(value, k)) {

v = walk(value, k);

if (v !== undefined) {

value[k] = v;

} else {

delete value[k];

}

}

}

}

return reviver.call(holder, key, value);

}

// Parsing happens in four stages. In the first stage, we replace certain

// Unicode characters with escape sequences. JavaScript handles many characters

// incorrectly, either silently deleting them, or treating them as line endings.

cx.lastIndex = 0;

if (cx.test(text)) {

text = text.replace(cx, function (a) {

return '\\u' + ('0000' +

(+(a.charCodeAt(0))).toString(16)).slice(-4);

});

}

// In the second stage, we run the text against regular expressions that look

// for non-JSON patterns. We are especially concerned with '()' and 'new'

// because they can cause invocation, and '=' because it can cause mutation.

// But just to be safe, we want to reject all unexpected forms.

// We split the second stage into 4 regexp operations in order to work around

// crippling inefficiencies in IE's and Safari's regexp engines. First we

// replace the JSON backslash pairs with '@' (a non-JSON character). Second, we

// replace all simple value tokens with ']' characters. Third, we delete all

// open brackets that follow a colon or comma or that begin the text. Finally,

// we look to see that the remaining characters are only whitespace or ']' or

// ',' or ':' or '{' or '}'. If that is so, then the text is safe for eval.

if (/^[\],:{}\s]*$/.

test(text.replace(/\\(?:["\\\/bfnrt]|u[0-9a-fA-F]{4})/g, '@').

replace(/"[^"\\\n\r]*"|true|false|null|-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/g, ']').

replace(/(?:^|:|,)(?:\s*\[)+/g, ''))) {

// In the third stage we use the eval function to compile the text into a

// JavaScript structure. The '{' operator is subject to a syntactic ambiguity

// in JavaScript: it can begin a block or an object literal. We wrap the text

// in parens to eliminate the ambiguity.

j = eval('(' + text + ')');

// In the optional fourth stage, we recursively walk the new structure, passing

// each name/value pair to a reviver function for possible transformation.

return typeof reviver === 'function' ?

walk({'': j}, '') : j;

}

// If the text is not JSON parseable, then a SyntaxError is thrown.

  throw new SyntaxError('JSON.parse');

}

};

}();

}

// Augment the basic prototypes if they have not already been augmented.

// These forms are obsolete. It is recommended that JSON.stringify and

// JSON.parse be used instead.

if (!Object.prototype.toJSONString) {

Object.prototype.toJSONString = function (filter) {

return JSON.stringify(this, filter);

};

Object.prototype.parseJSON = function (filter) {

return JSON.parse(this, filter);

};

} To run this example open the CreateMessage.htm onthe browser and the output on the browser will look like this:

 


Categories: JQUERY, JavaScript, Personal

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