Structures are the most versatile way to work with information sets. The structure contains a named set of elements, each of which is of a defined type. This type can be any of the types of data supported, or the type of a previously defined structure.

1 Server side script Objects

An object is a collection of related data that usually consists of some variables and functions, which are called properties and methods when they are inside objects. It is used to store a collection of defined data and more complex entities.

Properties are those that express a quality of the object, while methods are functionalities, that is, functions or modes of operation associated with an object.

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<xsql-script>
    <body>
        <set name='f_name'>Carlos</set>
        <set name='l_name'>González</set>
        <set name='code'>25701</set>
        <set name='country'>España</set>
        <set name='city'>Barcelona</set>
        
        <struct.declare type='s_user'>
            <field name='firstname'       type='string'  />
            <field name='lastname'        type='string'  />
            <field name='code'            type='integer' />
            <field name='country'         type='string'  />
            <field name='city'            type='string'  />
        </struct.declare>
            
        <set name='m_user' type='struct'>
            <struct type='s_user'>
                <string><f_name /></string>
                <string><l_name /></string>
                <number><code /></number>
                <string><country /></string>
                <string><city /></string>
            </struct>
        </set>
        
        <println><m_user /></println>
            
    </body>
</xsql-script>
struct.s_user
{
 s_user.firstname (1 - CHAR java.lang.String) = Carlos
 s_user.lastname (1 - CHAR java.lang.String) = González
 s_user.code (4 - INTEGER java.lang.Integer) = 25701
 s_user.country (1 - CHAR java.lang.String) = España
 s_user.city (1 - CHAR java.lang.String) = Barcelona
}
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var user = {
  firstName: 'Carlos',
  lastName: 'Gonzalez',
  code: 25701,
  country: 'España',
  city: 'Barcelona'
};

console.log(user);
{
  "firstName": "Carlos",
  "lastName": "González",
  "code": 25701,
  "country": "España",
  "city": "Barcelona"
}

1.1 Object properties

An object is created with an optional list of properties between "key-value", where the name of the property is always a string and its value can be any type of data, such as strings, numbers, booleans or complex data types like functions and other objects.

Properties whit functions

Properties with functions as their values are called methods to distinguish them from other properties.

To access a property you must use a valid variable name to extract directly to the property named by the value stored in the variable. Otherwise the code will return an error message indicating that the property is undefined.

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undefined field 'variable' on 'object'

An example of syntax to access the properties of an object is:

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<xsql-script>
    <body>
        <set name='f_name'>Carlos</set>
        <set name='l_name'>González</set>
        <set name='code'>25701</set>
        <set name='country'>España</set>
        <set name='city'>Barcelona</set>
        
        <struct.declare type='s_user'>
            <field name='firstname'       type='string'  />
            <field name='lastname'        type='string'  />
            <field name='code'            type='integer' />
            <field name='country'         type='string'  />
            <field name='city'            type='string'  />
        </struct.declare>
            
        <set name='m_user' type='struct'>
            <struct type='s_user'>
                <string><f_name /></string>
                <string><l_name /></string>
                <number><code /></number>
                <string><country /></string>
                <string><city /></string>
            </struct>
        </set>
        
        <println>He is <m_user.firstname /> <m_user.lastname /> and he lives in <m_user.city />, <m_user.country />.</println>
        
    </body>
</xsql-script>
He is Carlos González and he lives in Barcelona, España.
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var user = {
    firstName: 'Carlos',
    lastName: 'González',
    code: 25701,
    country: 'España',
    city: 'Barcelona'
};

console.log('He is ' + user.firstName, user.lastName + ' and he lives in ' + user.city +', ' + user.country +'.');
He is Carlos González and he lives in Barcelona, España.

1.1.1 Accessing Properties

The syntax for accessing the property of an object is:

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<xsql-script>
    <body>
        
        <struct.declare type='s_user'>
            <field name='firstname'       type='string'  />
            <field name='lastname'        type='string'  />
            <field name='code'            type='integer' />
            <field name='country'         type='string'  />
            <field name='city'            type='string'  />
        </struct.declare>
            
        <set name='m_user' type='struct'>
            <struct type='s_user'>
                <string>Manuel</string>
                <string>Perico</string>
                <number>33</number>
                <string>ES</string>
                <string>Barcelona</string>
            </struct>
        </set>
        
        <println><m_user.city /></println>
            
    </body>
</xsql-script>
Barcelona
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var mObjPerson = {
  "firstName": "Carlos",
  "lastName": "González",
  "country": "España",
  "code": 25701,
  "city": "Barcelona"
}


console.log(mObjPerson.city);        

console.log(mObjPerson["city"]); 

//expression
x = "city"; 
console.log(mObjPerson[x]);
Barcelona
Barcelona
Barcelona

1.1.2 Add/Delete properties

In XSQL Script it's not possible to add or remove a property from the declared structure.

The properties of an object can be removed or new ones can be added. The following example will show how to add and remove different properties of the user object

The delete operator deletes both the property and its value.

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<xsql-script>
    <!-- Not possible to add or remove a property. -->
</xsql-script>
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var person = {
    firstName: 'Carlos',
    lastName: 'González',
    code: 25701,
    country: 'España',
    city: 'Barcelona'
};

console.log(person); //Person before object

// Result of Add
person.academicTitle = "Engineer"; //Add object property
console.log(person); //Person after object

// Result of Delete
delete person.city; //Delete object property
console.log(person); //Person after object
//Person before object
{
  "firstName": "Carlos",
  "lastName": "González",
  "country": "España",
  "code": 25701,
  "city": "Barcelona"
}
// Result of Add
{
  "firstName": "Carlos",
  "lastName": "González",
  "country": "España",
  "code": 25701,
  "city": "Barcelona",
  "academicTitle": "Engineer"
}
// Result of Delete
{
  "firstName": "Carlos",
  "lastName": "González",
  "country": "España",
  "code": 25701,
  "academicTitle": "Engineer"
}

1.2 Object Methods

Methods are the functions that allow the object to do something or have something done to it. The difference between a function and a method is that, in a function, it's a self-contained unit of declarations and a method is attached to an object.

Methods can be useful to show the content of the object on the screen or to perform complex mathematical operations.

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<xsql-script>
    <body>
        <set name='f_name'>Carlos</set>
        <set name='l_name'>González</set>
        <set name='code'>25701</set>
        
        
        <struct.declare type='s_user'>
            <field name='firstname' type='string'  />
            <field name='lastname'  type='string'  />
            <field name='code'      type='integer' />
            <field name='lives'     type='string'><get_user /></field>
        </struct.declare>
        
        <function name='get_user'>
            <body>
                <return>
                    <set name='city'>Barcelona</set>
                    <set name='country'>España</set>
                </return>
            </body>
        </function>
        
        <set name='m_user' type='struct'>
            <struct type='s_user'>
                <string><f_name /></string>
                <string><l_name /></string>
                <number><code /></number>
                <get_user />
            </struct>
        </set>
        
        <println>He is <m_user.firstname /> <m_user.lastname /> and he lives in <get_user />.</println>
    
    </body>
</xsql-script>
He is Carlos González and he lives in [Barcelona,España].
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var user = {
    firstName: 'Carlos',
    lastName: 'González',
    code: 25701,
    country: 'España',
    city: 'Barcelona',
    lives = function() {
    return this.city + ", " + this.country;
    }
};

console.log('He is ' + user.firstName, user.lastName + ' and he lives in ' + user.lives() +'.');
He is Carlos González and he lives in Barcelona, España.

2 Object

In JavaScript, almost "everything" is an object.

  • Booleans can be objects (if defined with the new keyword)
  • Numbers can be objects (if defined with the new keyword)
  • Strings can be objects (if defined with the new keyword)
  • Dates are always objects
  • Maths are always objects
  • Regular expressions are always objects
  • Arrays are always objects
  • Functions are always objects
  • Objects are always objects

All JavaScript values, except primitives, are objects.

2.1 Server side script Primitives

A primitive value is a value that has no properties or methods.

A primitive data type is data that has a primitive value.

Server side cript defines 5 types of primitive data types:

  • string
  • number
  • boolean
  • null
  • undefined
Primitive values are immutable (they are hardcoded and therefore cannot be changed).
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<xsql-script>
    <body>
    
        <!--In XSQL all reference to an Object -->
        <!-- string is similar to string in server side script -->
        <set name='m_name' type='string'>Manuel</set>
        
        <!-- Class of type number are similar to number in server side script -->
        <set name='m_order' type='integer'>2</set>
        <set name='m_float' type='float'>2.03</set>
        <set name='m_decimal' type='decimal'>2.01</set>
        
        <!-- Class Boolean are similar to boolean in server side script -->
        <set name='m_is_false' type='boolean'><false /></set>
        
        <!-- Null is similar to null and undefined in server side script  -->
        <null name='m_null' />
    </body>
</xsql-script>
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// 
var mStrName = 'Manuel'; 
var mIntNumber = 2.03;
var mBoolFalse = false;
// null
var mIsNull = null;
// undefined
var mIsUndefined = undefined;

2.2 Single and multiple values objects

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<xsql-script>
    <body>
    
        <!-- single value -->
        <set name='m_name' type='string'>Manuel</set>
        
        <println><m_name /></println>
        <println />
        <!-- multiple value -->
        <struct.declare type='point3d'>
           <field name='x' type='integer' />
           <field name='y' type='integer' />
           <field name='z' type='integer' />
       </struct.declare>
       <set name='m_point'>
           <struct type='point3d'>
               <number>2</number>
               <number>4</number>
               <number>6</number>
           </struct>
       </set>
        
        <println><m_point /></println>
    </body>
</xsql-script>
Manuel

struct.point3d
{
 point3d.x (4 - INTEGER java.lang.Integer) = 2
 point3d.y (4 - INTEGER java.lang.Integer) = 4
 point3d.z (4 - INTEGER java.lang.Integer) = 6
}
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// single value 
var mStrName = 'Manuel';

console.log(mStrName);
console.log("");
// multiple value    
var mObjPoint3d = {
    x : 2, 
    y : 4,
    z : 6
}
   
console.log(mObjPoint3d);
Manuel

{
  "x": 2,
  "y": 4,
  "z": 6
}

2.3 Some examples of creating objects

Literally

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var mObjPoint3d = {x : 2, y : 4,z : 6}

console.log(mObjPoint3d);
{
  "x": 2,
  "y": 4,
  "z": 6
}

Spaces and line breaks are not important. An object definition can span multiple lines

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var mObjPoint3d = 
    {
        x : 2, 
        y : 4,
        z : 6
    }

console.log(mObjPoint3d);
{
  "x": 2,
  "y": 4,
  "z": 6
}

Creating with new Object() and adding properties

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var mObjPoint3d = new Object();
mObjPoint3d.x = 2;
mObjPoint3d.y = 4;
mObjPoint3d.z = 6;
console.log(mObjPoint3d);
{
  "x": 2,
  "y": 4,
  "z": 6
}

2.4 Objects are Mutable

Objects and structs are addressed by reference, not by value.

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<xsql-script>
    <body>
        <struct.declare type='s_car'>
            <field name='brand' type='string'  />
            <field name='model' type='string'  />
            <field name='power' type='integer' />
        </struct.declare>
            
        <set name='m_car1' type='struct'>
            <struct type='s_car'>
                <string>Siat</string>
                <string>Elebro</string>
                <number>100</number>
            </struct>
        </set>
        
        <set name='m_car2'><m_car1 /></set>
        <set name='m_car2.model'>Marbillo</set>
        
        <println>Car1: </println>
        <println><m_car1 /></println>
        <println>Car2: </println>
        <println><m_car2 /></println>   
    </body>
</xsql-script>
Car1: 
struct.s_car
{
 s_car.brand (1 - CHAR java.lang.String) = Siat
 s_car.model (1 - CHAR java.lang.String) = Marbillo
 s_car.power (4 - INTEGER java.lang.Integer) = 100
}
Car2: 
struct.s_car
{
 s_car.brand (1 - CHAR java.lang.String) = Siat
 s_car.model (1 - CHAR java.lang.String) = Marbillo
 s_car.power (4 - INTEGER java.lang.Integer) = 100
}
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var mObjCar = {
    brand : "Siat",
    model : "Elebro",
    power : 300
}

var mObjCar2 = mObjCar;
mObjCar.model = "Marbillo";           // This will change both mObjCar2.model and mObjCar.model

console.log("Car1:");
console.log(mObjCar2);
console.log("Car2:");
console.log(mObjCar);
Car1:
{
  "model": "Marbillo",
  "power": 300,
  "brand": "Siat"
}
Car2:
{
  "model": "Marbillo",
  "power": 300,
  "brand": "Siat"
}

2.5 Using JSON.stringify()

Many of server side script objects can be stringified (converted to a string) with the JavaScript function JSON.stringify():

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var mObjCar = {
    brand:"Fiot", 
    model: "Penda",
    power: 50
};

var mStrCar = JSON.stringify(mObjCar);

console.log(mStrCar);
{"brand":"Fiot","model":"Penda","power":50}

2.5.1 Stringify Dates

JSON.stringify converts dates into strings:

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var mObjCar = {
    brand : "Morcedes", 
    buy_date : new Date()
};
var mStrCar = JSON.stringify(mObjCar);

console.log(mStrCar);
{"brand":"Morcedes","buy_date":"2020-12-28T11:44:55.258Z"}

JSON.stringify remove Java objects from conversion to String:

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var mObjCar = {
    brand : "Morcedes", 
    buy_date : new Ax.util.Date()
};
var mStrCar = JSON.stringify(mObjCar);

console.log(mStrCar);

// you can use .toString() before to display
 mObjCar = {
    brand : "Morcedes", 
    buy_date : new Ax.util.Date().toString()
};

var mStrCar = JSON.stringify(mObjCar);

console.log(mStrCar);
{"brand":"Morcedes"}
{"brand":"Morcedes","buy_date":"Mon Dec 28 12:59:04 CET 2020"}

2.5.2 Stringify Functions

JSON.stringify will not stringify functions.

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var mObjCar = {
    brand : "Fiot", 
    age : function () {return 22;}
};
var mStrCar = JSON.stringify(mObjCar);
console.log(mStrCar);
{"brand":"Fiot"}

This can be "fixed" if you convert the functions into strings before stringifying

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var mObjCar = {
    brand : "Fiot", 
    age:function () {return 22;}
};
mObjCar.age = mObjCar.age.toString();
var mStrCar = JSON.stringify(mObjCar);
console.log(mStrCar);
{"brand" : "Fiot", "age" : "function () {return 22;}"}

2.5.3 Stringify Arrays

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var mArrFruits = ["Apple", "Orange", "Kiwy", "Grape"];

var mStrFruits = JSON.stringify(mArrFruits);

console.log(mStrFruits)
["Apple","Orange","Kiwy","Grape"]

3 Object Constructors

Copy 
<xsql-script>
    <body>
        <struct.declare type='s_car'>
            <field name='brand' type='string'  />
            <field name='model' type='string'  />
            <field name='age'   type='integer'  />
            <field name='power' type='integer' />
        </struct.declare>
            
        <set name='m_car1' type='struct'>
            <struct type='s_car'>
                <string>Soat</string>
                <string>Lacon</string>
                <number>2</number>
                <number>150</number>
            </struct>
        </set>
        
        <set name='m_car2' type='struct'>
            <struct type='s_car'>
                <string>Feat</string>
                <string>Rally</string>
                <number>23</number>
                <number>58</number>
            </struct>
        </set>
        
        <println>Car1: </println>
        <println><m_car1 /></println>
        <println>Car2: </println>
        <println><m_car2 /></println>   
    </body>
</xsql-script>
Car1: 
struct.s_car
{
 s_car.brand (1 - CHAR java.lang.String) = Soat
 s_car.model (1 - CHAR java.lang.String) = Lacon
 s_car.age (4 - INTEGER java.lang.Integer) = 2
 s_car.power (4 - INTEGER java.lang.Integer) = 150
}
Car2: 
struct.s_car
{
 s_car.brand (1 - CHAR java.lang.String) = Feat
 s_car.model (1 - CHAR java.lang.String) = Rally
 s_car.age (4 - INTEGER java.lang.Integer) = 23
 s_car.power (4 - INTEGER java.lang.Integer) = 58
}
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function Car(brand, model, age, power) {
    this.brand = brand;
    this.model = model;
    this.age = age;
    this.power = power;
}

// Objects of the same type are created by calling the constructor function with the new keyword
var car1 = new Car("Soat", "Lacon", 2, 150);
var car2 = new Car("Feat", "Rally", 23, 58);

console.log("Car1:");
console.log(car1);
console.log("Car2:");
console.log(car2);
Car1:
{
  "model": "Lacon",
  "power": 150,
  "brand": "Soat",
  "age": 2
}
Car2:
{
  "model": "Rally",
  "power": 58,
  "brand": "Feat",
  "age": 23
}

3.1 The this Keyword

This is used in server side script to refer to the object, class, or other entity of which the currently running code is a part. The entity referred to by these keywords thus depends on the execution context (such as which object is having its method called). Different programming languages use these keywords in slightly different ways. In languages where a keyword like "this" is mandatory, the keyword is the only way to access data and methods stored in the current object. Where optional, they can disambiguate variables and functions with the same name.

Note that this is not a variable. It is a keyword. You cannot change the value of this.

3.2 Adding a Property to an Object

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var mObjCar1 = 
{
  model : "Lacon",
  power : 150,
  brand : "Soat"
}
mObjCar1.age = 2;

console.log(mObjCar1);
{
  "model": "Lacon",
  "power": 150,
  "brand": "Soat",
  "age": 2
}

3.3 Adding a Property to an Object

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var mObjCar1 = 
{
  model : "Lacon",
  power : 150,
  brand : "Soat"
}


mObjCar1.logo = function () {
  return this.brand+ " " + this.model;
};

console.log(mObjCar1.logo());
Soat Lacon

3.4 Built-in server side script Constructors

Server side script has built-in constructors for native objects:

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var mObj1 = new Object();    // A new Object object
var mStr1 = new String();    // A new String object
var mNum1 = new Number();    // A new Number object
var mBool1 = new Boolean();   // A new Boolean object
var mArr1 = new Array();     // A new Array object
var mReg1 = new RegExp();    // A new RegExp object
var mFun1 = new Function();  // A new Function object
var mDate1 = new Date();      // A new Date object

var mObj2 = {};            // new object
var mStr2 = "";            // new primitive string
var mNum3 = 0;             // new primitive number
var mBool3 = false;         // new primitive boolean
var mArr3 = [];            // new array object
var mReg3 = /()/           // new regexp object
var mFun3 = function(){};  // new function object

Strings, numbers and booleans are created as primitives.

But strings, numbers and booleans can also be created as objects using the new keyword

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var mStrName = "John";             //string primitive
var mStrName = new String("John"); // String Object
var mNumberX = 123;                // String primitive
var mNumberX = new Number(123);    // String primitive
var mBoolX = false;                // Boolean primitive
var mBoolX= new Boolean(false);    // Boolean object