Javascript Object Literals

Basic syntax:

   anyvar = "value";
   array  = [item,item,item];
   list   = {0:value, 1:value};
   map    = {key:value, key:value};
   object = {key:value, key:[array...], key:{map...}};
   table  = [[array...], [array...]];
   fault  = {error:123, text:'Something very bad happened'};

The easiest way to exchange JavaScript objects is to generate a stream on the server in the following PHP example:

<?php
header('Content-type: text/plain');
echo "person={name:'Britney', age:22, active:true}";
?>

then eval() the responseText from an XMLHttpRequest call in the client assigning it to an object for later use:

   var data = eval(responseText);
   alert(data.person.name);

Primitives: string, number, bool, null

   var1 = "britney";
   var2 = 123;
   var3 = true;
   var4 = null;
   write(var1);

Array or list

   var1 = [111,222,333];       // homogeneous
   var2 = ['britney',22,true]; // heterogeneous
   write(var1[0]);
   write(var2[0]);

An array is a map with numeric keys

   var1 = {0:111, 1:222, 2:333};       // homogeneous
   var2 = {0:'britney', 1:22, 2:true}; // heterogeneous
   write(var1[0]);
   write(var2[0]);

Map/object/hash/struct: an array with named keys

   var1 = {name:'britney', age:22, active:true};
   write(var1['name']);
   write(var1.name);

Complex object: mixed structures

   person = {
       name:'britney', 
       age:22, 
       address:{
           city:'Sunny', 
           state:'FL'
       },
       phones:['555-1234','555-1235']
   };
   write(person.name);
   write(person.address.city);
   write(person.phones[0]);

Table: a 2D array

   data = [
       ['britney', 22, true , '555-1234'],
       ['avril'  , 19, false, '555-4321'],
       ['christy', 21, true , '555-9876']
   ];
   write(data[0][0]);

Table: a list of arrays

   data = {
       0:['britney', 22, true , '555-1234'],
       1:['avril'  , 19, false, '555-4321'],
       2:['christy', 21, true , '555-9876']
   };
   write(data[0][0]);

Mapped Table: a list of structs

   data = {
       0:{name:'britney', age:22, active:true},
       1:{name:'avril'  , age:19, active:false},
       2:{name:'christy', age:21, active:true}
   };
   write(data[0]['name']);
   write(data[0].name);

or

   row = data[0];
   write(row.name);

Typed Table: a table with header structure

   data = {
       colcount:3,
       rowcount:3,
       cols:[
           ['name'  , 'string' , 40, 0, false],
           ['age'   , 'integer',  8, 0, true ],
           ['active', 'boolean',  1, 0, true ]
       ],
       rows:[
           ['britney', 22, true ],
           ['avril'  , 19, false],
           ['christy', 21, true ]
       ]
   };
   write(data.colcount);
   write(data.cols[0][0]);
   write(data.rows[0][0]);

Datasets: a group of tables

   dataset = {
       tables:{
           customers:{
               cols:[ /*here*/ ],
               rows:[ /*here*/ ]
           },
           orders:{
               cols:[ /*here*/ ],
               rows:[ /*here*/ ]
           }
       },
       relations:{
           0:{
               parent:'customers', 
               child:'orders', 
               keyparent:'custid', 
               keychild:'orderid',
               onetomany:true
           }
       }
   }

Faults

Whenever there is a problem on the server side, it is a good practice to report an exception in the form of:

   fault = {error:401, text:'Data source not available'};
   fault = {error:501, text:'You have no rights to access that data'};

then, on the client side, eval() and test for errors in the response:

function myStuff(response){
   var data = eval(response);
   if(data.error){
      alert(data.text);
   }else{
     doStuffWith(data);
   }

Well folks, we have covered everything you should know to get you up and running. I hope you have enjoyed this introductory essay on JavaScript Object Literals. George Nava - 2005.11.11