JavaScript language

JavaScript is used by VRML to add more interactivity in VRML scene.
More information about JavaScript language: http://en.wikipedia.org/wiki/Javascript.

JavaScript is supported by VRML via the Script node.
The url property contains JavaScript code.
Script node interface:

Script {
  SFString url ""
}

Example:

#VRML V2.0 utf8

DEF script Script {
  url "javascript:
    function myFunction (value) {
      Browser.print ('value = ' + value);
    }
  "
}

Note:
JavaScript code starts by javascript: (but it is not required).

Warning:
Don't use " (quotation mark) character in JavaScript part (functions, comments, ...).
This character is used to close the url property of Script node.
Example:
Browser.print("hello world"); // Syntax error
Browser.print('hello world'); // Valid code

Fields are used to:

declare global variable (JavaScript code cannot contain global variable).
access to scene node (access to scene node require a field).

Field declaration syntax:

# Field declaration
field <type> <name> <default_value>
# Node declaration
field SFNode <name> USE <node_name>

<type>:
Field type (SFString, MFString, SFInt32, MFInt32, SFFloat, MFFloat, SFBool, SFTime, ...).

Note:
Use SFNode to link a node with a script variable.

<name>:
Field name. This name is used in JavaScript.

<default_value>:
Default field value. Default value is not required.

<node_name>:
Node name (defined by DEF <node name> in VRML scene).
To use a VRML node in JavaScript function.

Example:

#VRML V2.0 utf8
Shape {
  appearance Appearance { material Material2D { emissiveColor 0 0 0 } }
  geometry DEF TEXT WrapText { string [ "initial text" ] }
}
DEF script Script {
  field SFNode textNode USE TEXT
  field SFString globalVar ""
  url "javascript:
    function myFunction (value) {
      textNode.string[0] = value;
      globalVar = value;
    }
  "
}

Comments

MeMo use // to introduce a line of comment.

Warning:
Multi-line comments are not supported by MeMo.

Note:
Comments are removed during M4M compilation. Feel free to comment your code!

Comments syntax:

// my comment

Functions

MeMo use the same syntax than JavaScript to declare and use a function.
Use return keyword to return a value.
Function declaration syntax:

function <function_name> (<params>) {
  //Function
}

<function_name>:
Name of function.
<params>:
List of function parameters with comma separator.

Example:

function functionWithoutParameter () {
  //Do nothing
}
function functionWith3Parameters (param1, param2, param3) {
  //Write parameters on output
  Browser.print('parameters : ' + param1 + ' / ' + param2 + ' / ' + param3);
}
function functionWithReturn () {
  //Return PI
  return 3.1415;
}
function add (value1, value2) {
  //Return addition of parameters
  return value1 + value2;
}

initialize() function

initialize() function is called when scene is loaded.
We use this function to initialize VRML scene.
Example:

function initialize () {
  Browser.print('Scene initialization...');
}

Local variables

Variables are declared only in function (local variable).
We cannot declare global variable (use field if global variables are required).
Function declaration syntax:

var <var_name>;
var <var_name> = <value>;

<var_name>:
Variable name.
<value>:
Variable value.

Process events in JavaScript

VRML use ROUTE keyword to manage events.
We can use JavaScript to send an event or receive and process this event.
Events declaration syntax is same than field declarations. We use eventIn and eventOut keyword to replace field keyword.

To receive and process an event:

declare an eventIn field in Script node.
declare a function with the same event name.
we receive data in function parameters or in function name.

Example:

DEF MYSCRIPT Script {
  #Define event in with integer type
  eventIn SFInt32 myEvent
  url "javascript:
    //Process event when myEvent is received
    function myEvent(value) {
      //value contains an integer
      Browser.print ( 'Receive value :' + value);
    }
  "
}
#Route an event on OTHER node to myEvent function
ROUTE OTHER.valueChange TO MYSCRIPT.myEvent

To send an event:

declare an eventOut field in Script node.
change eventOut value in a function.

Example:

DEF MYSCRIPT Script {
  #Define event out with integer type
  eventOut SFInt32 myEvent 0
  url "javascript:
    //Initialize the scene
    //Send event during initialization
    function initialize () {
      //Send myEvent (change the value)
      myEvent = 1;
    }
  "
}
#Route myEvent function to another node value
ROUTE MYSCRIPT.myEvent TO OTHER.scriptIsInitialized

JavaScript libraries

To advanced use, we can use JavaScript libraries.
See JavaScript reference chapter.

Class declarations

MeMo doesn't support class declaration.
We cannot describe and use personal classes.
Solution: Use a VRML prototype.

Create a node with JavaScript

We cannot create VRML nodes dynamically with MeMo.

Other

More:
See FAQ for more restrictions.