JSON.stringify

var contact = new Object(); 
contact.firstname = "Jesper"; 
contact.surname = "Aaberg"; 
contact.phone = ["555-0100", "555-0120"]; 
 
var memberfilter = new Array(); 
memberfilter[0] = "surname"; 
memberfilter[1] = "phone"; 
var jsonText = JSON.stringify(contact, memberfilter, "\t"); 
document.write(jsonText); 

// Output:  
// { "surname": "Aaberg", "phone": [ "555-0100", "555-0120" ] }

var continents = new Array(); 
continents[0] = "Europe"; 
continents[1] = "Asia"; 
continents[2] = "Australia"; 

var jsonText = JSON.stringify(continents, replaceToUpper); 
 
function replaceToUpper(key, value) { 
    return value.toString().toUpperCase(); 
} 
document.write(jsonText); 
 
//Output: 
// "EUROPE,ASIA,AUSTRALIA" 

var contact = new Object();  
contact.firstname = "Jesper"; 
contact.surname = "Aaberg"; 
contact.phone = ["555-0100", "555-0120"]; 
 
contact.toJSON = function(key) 
 { 
    var replacement = new Object(); 
    for (var val in this) 
    { 
        if (typeof (this[val]) === ‘string‘) 
            replacement[val] = this[val].toUpperCase(); 
        else 
            replacement[val] = this[val] 
    } 
    return replacement; 
}; 
 
var jsonText = JSON.stringify(contact); 
document.write(jsonText); 
 
// Output: 
//{"firstname":"JESPER","surname":"AABERG","phone":["555-0100","555-0120"]}