Javascript script load and execution - Revision history

Marian: /* Script (re)entry points */

2024-09-03T05:54:04Z

‎Script (re)entry points

Marian: /* Script context initialize */

2024-09-02T14:06:18Z

‎Script context initialize

Marian at 13:58, 2 September 2024

2024-09-02T13:58:59Z

Marian at 13:58, 2 September 2024

2024-09-02T13:58:42Z

Marian at 13:58, 2 September 2024

2024-09-02T13:58:06Z

Marian: /* Script (re)entry points */

2024-09-02T13:57:19Z

‎Script (re)entry points

Marian: /* Script context initialize */

2024-09-02T13:56:04Z

‎Script context initialize

Marian: Created page with " == Code and context (data) == Code is the internal structure holding the instructions parsed on script load.
Code won't change during script run. Context is the inter..."

2024-09-02T13:55:32Z

Created page with " == Code and context (data) == Code is the internal structure holding the instructions parsed on script load. Code won't change during script run. Context is the inter..."

New page

== Code and context (data) ==

Code is the internal structure holding the instructions parsed on script load. 
Code won't change during script run.

Context is the internal structure holding all variables created during script run. 
Variables created in one context are only available in script using it. 

== Script context initialize ==

Each time a context is created the module will do the following:
* Push native objects and functions into the context:
** Standard Javascript objects ('''Object''', '''Array''', '''XML''', '''RegExp''', '''JPath''', ...)
** Standard Javascript functions ('''parseInt''', '''isNaN''', ...)
** Yate objects ('''Engine''', '''Message''', '''ConfigFile''' ...)
* Send a ''script.init'' message to allow other modules to push extensions (custom native objects) into the context. This is controlled by javascript configuration and specific context (e.g. may be disabled when a message singleton context is created). 
* Run the script

Example:
// Script run. Function call
Engine.debugName("name");
// Script run. Create a global variable
debug = Engine.debugEnabled();
// Script run. Check if some extension object named SomeObject was inserted into the context during script init
if (SomeObject.initialize)
SomeObject.initialize();
// Function definition
function callback() {
// code ...
}
// Script run. Set callback to process
Engine.setInterval(callback,1000);

'''WARNING: A runtime error (invalid function call ...) occurring during script run will fail script load. If context is a singleton one the callback won't be called.'''

== Singleton context ==
A singleton context means a context created when handling a message and handler was installed using a singleton handler or processing a message singleton post hook. 
The code is the same as the one of the script installing the handler or post hook. 
Processing: 
# Initialize (see section above)
# Call the callback function
# Delete the singleton context

Example:
function callback() {
// code ...
}
if (Engine.installSingleton) {
// Context is run in main script
Engine.debugName("test");
Engine.debugLevel("level 10");
debug = true;
Message.installSingleton(callback,"test","some_message_name");
}
else {
// Context is run in message handler: separate context. The javascript module will call the callback function after script init
// Debug data (name, level) is automatically set by javascript module from main script
debug = Engine.debugEnabled();
}

== Script (re)entry points ==

Entry points are functions called by javascript module: 
* When a message handler is installed and it receives a message. See Message.install() and Message.installSingleton()
* When a timer was set and its interval elapsed. See Engine.setInterval() and Engine.setTimeout()
* When an installed event is triggered. See Engine.setEvent()
* When javascript module calls the ''onUnload'' function (this function is called when script is unloaded if defined in the context)
* When a message was enqueued and a callback was given. See Message.enqueue()
* When a message post hook is installed and it receives a message. See Message.installPostHook() and Message.installPostHookSingleton()
* When a message hook was installed. See Message.installHook()

Re-entry points are locations where context is unblocked and code execution is resumed after function call: 
* Message dispatch(true)
* Engine.sleep(), Engine.usleep(), Engine.idle(), Engine.yield()
* Semaphore wait()
* DNS.query()

On each (re)entry point the context mutex is locked. 
The script context should be re-checked for variable presence. 

'''WARNING:''' 
'''A runtime error (invalid function call ...) occurring in entry point code will fail the callback function call. '''
'''Execution returns in C++ code regardless function call stack. '''
'''If entry point is a message handler false will be returned to caller. '''

Example:
function callback(msg) {
var m = new Message("database");
// set params ...
var ok = m.dispatch(true);
// The Engine object will no longer be available if script is unloaded during database query
if (!Engine)
return false;
Engine.debug(Engine.DebugNote,"Some text");
}
Message.install(callback,"some_message_name");

== See also ==

* [[Javascript]]
* [[Javascript Message]]
* [[Javascript Engine]]

[[Category:Javascript]] [[Category:Programmers]] [[Category:Scripting]]

@@ Line 16: / Line 16: @@
 ** Standard Javascript objects ('''Object''', '''Array''', '''XML''', '''RegExp''', ...)
 ** Standard Javascript functions ('''parseInt''', '''isNaN''', ...)
 ** Yate specific objects ('''Engine''', '''Message''', '''ConfigFile''' ...)
 * Dispatch a ''script.init'' message to allow other modules to push extensions (custom native objects) into the context.<br/>This is controlled by javascript configuration and specific context (e.g. may be disabled when a message singleton context is created).<br/>

@@ Line 16: / Line 16: @@
 ** Standard Javascript objects ('''Object''', '''Array''', '''XML''', '''RegExp''', ...)
 ** Standard Javascript functions ('''parseInt''', '''isNaN''', ...)
-** Yate objects ('''Engine''', '''Message''', '''ConfigFile''' ...)
+** Yate specific objects ('''Engine''', '''Message''', '''ConfigFile''' ...)
 * Dispatch a ''script.init'' message to allow other modules to push extensions (custom native objects) into the context.<br/>This is controlled by javascript configuration and specific context (e.g. may be disabled when a message singleton context is created).<br/>
 * Run the script

@@ Line 54: / Line 54: @@
 * Engine.sleep(), Engine.usleep(), Engine.idle(), Engine.yield()
 * Semaphore wait()
-* DNS.query()
+* DNS.query() requesting non blocking operation
@@ Line 77: / Line 77: @@
+  }
   Message.install(callback,"some_message_name");
 == Singleton context ==

@@ Line 14: / Line 14: @@
 Each time a context is created the module will do the following:
 * Push native objects and functions into the context:
-** Standard Javascript objects ('''Object''', '''Array''', '''XML''', '''RegExp''', '''JPath''', ...)
+** Standard Javascript objects ('''Object''', '''Array''', '''XML''', '''RegExp''', ...)
 ** Standard Javascript functions ('''parseInt''', '''isNaN''', ...)
 ** Yate objects ('''Engine''', '''Message''', '''ConfigFile''' ...)

@@ Line 37: / Line 37: @@
 '''WARNING: A runtime error (invalid function call ...) occurring during script run will fail script load. If context is a singleton one the callback won't be called.'''
 == Script (re)entry points ==
@@ Line 101: / Line 76: @@
+  }
   Message.install(callback,"some_message_name");
 == See also ==

Javascript script load and execution - Revision history

Marian: /* Script (re)entry points */

Marian: /* Script context initialize */

Marian at 13:58, 2 September 2024

Marian at 13:58, 2 September 2024

Marian at 13:58, 2 September 2024

Marian: /* Script (re)entry points */

Marian: /* Script context initialize */

Marian: Created page with " == Code and context (data) == Code is the internal structure holding the instructions parsed on script load. Code won't change during script run. Context is the inter..."

Marian: Created page with " == Code and context (data) == Code is the internal structure holding the instructions parsed on script load.
Code won't change during script run. Context is the inter..."