summaryrefslogtreecommitdiffstats
path: root/DOCS/man/javascript.rst
diff options
context:
space:
mode:
Diffstat (limited to 'DOCS/man/javascript.rst')
-rw-r--r--DOCS/man/javascript.rst398
1 files changed, 398 insertions, 0 deletions
diff --git a/DOCS/man/javascript.rst b/DOCS/man/javascript.rst
new file mode 100644
index 0000000..bdbb04b
--- /dev/null
+++ b/DOCS/man/javascript.rst
@@ -0,0 +1,398 @@
+JAVASCRIPT
+==========
+
+JavaScript support in mpv is near identical to its Lua support. Use this section
+as reference on differences and availability of APIs, but otherwise you should
+refer to the Lua documentation for API details and general scripting in mpv.
+
+Example
+-------
+
+JavaScript code which leaves fullscreen mode when the player is paused:
+
+::
+
+ function on_pause_change(name, value) {
+ if (value == true)
+ mp.set_property("fullscreen", "no");
+ }
+ mp.observe_property("pause", "bool", on_pause_change);
+
+
+Similarities with Lua
+---------------------
+
+mpv tries to load a script file as JavaScript if it has a ``.js`` extension, but
+otherwise, the documented Lua options, script directories, loading, etc apply to
+JavaScript files too.
+
+Script initialization and lifecycle is the same as with Lua, and most of the Lua
+functions at the modules ``mp``, ``mp.utils``, ``mp.msg`` and ``mp.options`` are
+available to JavaScript with identical APIs - including running commands,
+getting/setting properties, registering events/key-bindings/hooks, etc.
+
+Differences from Lua
+--------------------
+
+No need to load modules. ``mp``, ``mp.utils``, ``mp.msg`` and ``mp.options``
+are preloaded, and you can use e.g. ``var cwd = mp.utils.getcwd();`` without
+prior setup.
+
+Errors are slightly different. Where the Lua APIs return ``nil`` for error,
+the JavaScript ones return ``undefined``. Where Lua returns ``something, error``
+JavaScript returns only ``something`` - and makes ``error`` available via
+``mp.last_error()``. Note that only some of the functions have this additional
+``error`` value - typically the same ones which have it in Lua.
+
+Standard APIs are preferred. For instance ``setTimeout`` and ``JSON.stringify``
+are available, but ``mp.add_timeout`` and ``mp.utils.format_json`` are not.
+
+No standard library. This means that interaction with anything outside of mpv is
+limited to the available APIs, typically via ``mp.utils``. However, some file
+functions were added, and CommonJS ``require`` is available too - where the
+loaded modules have the same privileges as normal scripts.
+
+Language features - ECMAScript 5
+--------------------------------
+
+The scripting backend which mpv currently uses is MuJS - a compatible minimal
+ES5 interpreter. As such, ``String.substring`` is implemented for instance,
+while the common but non-standard ``String.substr`` is not. Please consult the
+MuJS pages on language features and platform support - https://mujs.com .
+
+Unsupported Lua APIs and their JS alternatives
+----------------------------------------------
+
+``mp.add_timeout(seconds, fn)`` JS: ``id = setTimeout(fn, ms)``
+
+``mp.add_periodic_timer(seconds, fn)`` JS: ``id = setInterval(fn, ms)``
+
+``utils.parse_json(str [, trail])`` JS: ``JSON.parse(str)``
+
+``utils.format_json(v)`` JS: ``JSON.stringify(v)``
+
+``utils.to_string(v)`` see ``dump`` below.
+
+``mp.get_next_timeout()`` see event loop below.
+
+``mp.dispatch_events([allow_wait])`` see event loop below.
+
+Scripting APIs - identical to Lua
+---------------------------------
+
+(LE) - Last-Error, indicates that ``mp.last_error()`` can be used after the
+call to test for success (empty string) or failure (non empty reason string).
+Where the Lua APIs use ``nil`` to indicate error, JS APIs use ``undefined``.
+
+``mp.command(string)`` (LE)
+
+``mp.commandv(arg1, arg2, ...)`` (LE)
+
+``mp.command_native(table [,def])`` (LE)
+
+``id = mp.command_native_async(table [,fn])`` (LE) Notes: ``id`` is true-thy on
+success, ``error`` is empty string on success.
+
+``mp.abort_async_command(id)``
+
+``mp.del_property(name)`` (LE)
+
+``mp.get_property(name [,def])`` (LE)
+
+``mp.get_property_osd(name [,def])`` (LE)
+
+``mp.get_property_bool(name [,def])`` (LE)
+
+``mp.get_property_number(name [,def])`` (LE)
+
+``mp.get_property_native(name [,def])`` (LE)
+
+``mp.set_property(name, value)`` (LE)
+
+``mp.set_property_bool(name, value)`` (LE)
+
+``mp.set_property_number(name, value)`` (LE)
+
+``mp.set_property_native(name, value)`` (LE)
+
+``mp.get_time()``
+
+``mp.add_key_binding(key, name|fn [,fn [,flags]])``
+
+``mp.add_forced_key_binding(...)``
+
+``mp.remove_key_binding(name)``
+
+``mp.register_event(name, fn)``
+
+``mp.unregister_event(fn)``
+
+``mp.observe_property(name, type, fn)``
+
+``mp.unobserve_property(fn)``
+
+``mp.get_opt(key)``
+
+``mp.get_script_name()``
+
+``mp.get_script_directory()``
+
+``mp.osd_message(text [,duration])``
+
+``mp.get_wakeup_pipe()``
+
+``mp.register_idle(fn)``
+
+``mp.unregister_idle(fn)``
+
+``mp.enable_messages(level)``
+
+``mp.register_script_message(name, fn)``
+
+``mp.unregister_script_message(name)``
+
+``mp.create_osd_overlay(format)``
+
+``mp.get_osd_size()`` (returned object has properties: width, height, aspect)
+
+``mp.msg.log(level, ...)``
+
+``mp.msg.fatal(...)``
+
+``mp.msg.error(...)``
+
+``mp.msg.warn(...)``
+
+``mp.msg.info(...)``
+
+``mp.msg.verbose(...)``
+
+``mp.msg.debug(...)``
+
+``mp.msg.trace(...)``
+
+``mp.utils.getcwd()`` (LE)
+
+``mp.utils.readdir(path [, filter])`` (LE)
+
+``mp.utils.file_info(path)`` (LE) Note: like lua - this does NOT expand
+meta-paths like ``~~/foo`` (other JS file functions do expand meta paths).
+
+``mp.utils.split_path(path)``
+
+``mp.utils.join_path(p1, p2)``
+
+``mp.utils.subprocess(t)``
+
+``mp.utils.subprocess_detached(t)``
+
+``mp.utils.get_env_list()``
+
+``mp.utils.getpid()`` (LE)
+
+``mp.add_hook(type, priority, fn(hook))``
+
+``mp.options.read_options(obj [, identifier [, on_update]])`` (types:
+string/boolean/number)
+
+Additional utilities
+--------------------
+
+``mp.last_error()``
+ If used after an API call which updates last error, returns an empty string
+ if the API call succeeded, or a non-empty error reason string otherwise.
+
+``Error.stack`` (string)
+ When using ``try { ... } catch(e) { ... }``, then ``e.stack`` is the stack
+ trace of the error - if it was created using the ``Error(...)`` constructor.
+
+``print`` (global)
+ A convenient alias to ``mp.msg.info``.
+
+``dump`` (global)
+ Like ``print`` but also expands objects and arrays recursively.
+
+``mp.utils.getenv(name)``
+ Returns the value of the host environment variable ``name``, or
+ ``undefined`` if the variable is not defined.
+
+``mp.utils.get_user_path(path)``
+ Trivial wrapper of the ``expand-path`` mpv command, returns a string.
+ ``read_file``, ``write_file``, ``append_file`` and ``require`` already
+ expand the path internally and accept mpv meta-paths like ``~~desktop/foo``.
+
+``mp.utils.read_file(fname [,max])``
+ Returns the content of file ``fname`` as string. If ``max`` is provided and
+ not negative, limit the read to ``max`` bytes.
+
+``mp.utils.write_file(fname, str)``
+ (Over)write file ``fname`` with text content ``str``. ``fname`` must be
+ prefixed with ``file://`` as simple protection against accidental arguments
+ switch, e.g. ``mp.utils.write_file("file://~/abc.txt", "hello world")``.
+
+``mp.utils.append_file(fname, str)``
+ Same as ``mp.utils.write_file`` if the file ``fname`` does not exist. If it
+ does exist then append instead of overwrite.
+
+Note: ``read_file``, ``write_file`` and ``append_file`` throw on errors, allow
+text content only.
+
+``mp.get_time_ms()``
+ Same as ``mp.get_time()`` but in ms instead of seconds.
+
+``mp.get_script_file()``
+ Returns the file name of the current script.
+
+``exit()`` (global)
+ Make the script exit at the end of the current event loop iteration.
+ Note: please remove added key bindings before calling ``exit()``.
+
+``mp.utils.compile_js(fname, content_str)``
+ Compiles the JS code ``content_str`` as file name ``fname`` (without loading
+ anything from the filesystem), and returns it as a function. Very similar
+ to a ``Function`` constructor, but shows at stack traces as ``fname``.
+
+``mp.module_paths``
+ Global modules search paths array for the ``require`` function (see below).
+
+Timers (global)
+---------------
+
+The standard HTML/node.js timers are available:
+
+``id = setTimeout(fn [,duration [,arg1 [,arg2...]]])``
+
+``id = setTimeout(code_string [,duration])``
+
+``clearTimeout(id)``
+
+``id = setInterval(fn [,duration [,arg1 [,arg2...]]])``
+
+``id = setInterval(code_string [,duration])``
+
+``clearInterval(id)``
+
+``setTimeout`` and ``setInterval`` return id, and later call ``fn`` (or execute
+``code_string``) after ``duration`` ms. Interval also repeat every ``duration``.
+
+``duration`` has a minimum and default value of 0, ``code_string`` is
+a plain string which is evaluated as JS code, and ``[,arg1 [,arg2..]]`` are used
+as arguments (if provided) when calling back ``fn``.
+
+The ``clear...(id)`` functions cancel timer ``id``, and are irreversible.
+
+Note: timers always call back asynchronously, e.g. ``setTimeout(fn)`` will never
+call ``fn`` before returning. ``fn`` will be called either at the end of this
+event loop iteration or at a later event loop iteration. This is true also for
+intervals - which also never call back twice at the same event loop iteration.
+
+Additionally, timers are processed after the event queue is empty, so it's valid
+to use ``setTimeout(fn)`` as a one-time idle observer.
+
+CommonJS modules and ``require(id)``
+------------------------------------
+
+CommonJS Modules are a standard system where scripts can export common functions
+for use by other scripts. Specifically, a module is a script which adds
+properties (functions, etc) to its pre-existing ``exports`` object, which
+another script can access with ``require(module-id)``. This runs the module and
+returns its ``exports`` object. Further calls to ``require`` for the same module
+will return its cached ``exports`` object without running the module again.
+
+Modules and ``require`` are supported, standard compliant, and generally similar
+to node.js. However, most node.js modules won't run due to missing modules such
+as ``fs``, ``process``, etc, but some node.js modules with minimal dependencies
+do work. In general, this is for mpv modules and not a node.js replacement.
+
+A ``.js`` file extension is always added to ``id``, e.g. ``require("./foo")``
+will load the file ``./foo.js`` and return its ``exports`` object.
+
+An id which starts with ``./`` or ``../`` is relative to the script or module
+which ``require`` it. Otherwise it's considered a top-level id (CommonJS term).
+
+Top-level id is evaluated as absolute filesystem path if possible, e.g. ``/x/y``
+or ``~/x``. Otherwise it's considered a global module id and searched according
+to ``mp.module_paths`` in normal array order, e.g. ``require("x")`` tries to
+load ``x.js`` at one of the array paths, and id ``foo/x`` tries to load ``x.js``
+inside dir ``foo`` at one of the paths.
+
+The ``mp.module_paths`` array is empty by default except for scripts which are
+loaded as a directory where it contains one item - ``<directory>/modules/`` .
+The array may be updated from a script (or using custom init - see below) which
+will affect future calls to ``require`` for global module id's which are not
+already loaded/cached.
+
+No ``global`` variable, but a module's ``this`` at its top lexical scope is the
+global object - also in strict mode. If you have a module which needs ``global``
+as the global object, you could do ``this.global = this;`` before ``require``.
+
+Functions and variables declared at a module don't pollute the global object.
+
+Custom initialization
+---------------------
+
+After mpv initializes the JavaScript environment for a script but before it
+loads the script - it tries to run the file ``init.js`` at the root of the mpv
+configuration directory. Code at this file can update the environment further
+for all scripts. E.g. if it contains ``mp.module_paths.push("/foo")`` then
+``require`` at all scripts will search global module id's also at ``/foo``
+(do NOT do ``mp.module_paths = ["/foo"];`` because this will remove existing
+paths - like ``<script-dir>/modules`` for scripts which load from a directory).
+
+The custom-init file is ignored if mpv is invoked with ``--no-config``.
+
+Before mpv 0.34, the file name was ``.init.js`` (with dot) at the same dir.
+
+The event loop
+--------------
+
+The event loop poll/dispatch mpv events as long as the queue is not empty, then
+processes the timers, then waits for the next event, and repeats this forever.
+
+You could put this code at your script to replace the built-in event loop, and
+also print every event which mpv sends to your script:
+
+::
+
+ function mp_event_loop() {
+ var wait = 0;
+ do {
+ var e = mp.wait_event(wait);
+ dump(e); // there could be a lot of prints...
+ if (e.event != "none") {
+ mp.dispatch_event(e);
+ wait = 0;
+ } else {
+ wait = mp.process_timers() / 1000;
+ if (wait != 0) {
+ mp.notify_idle_observers();
+ wait = mp.peek_timers_wait() / 1000;
+ }
+ }
+ } while (mp.keep_running);
+ }
+
+
+``mp_event_loop`` is a name which mpv tries to call after the script loads.
+The internal implementation is similar to this (without ``dump`` though..).
+
+``e = mp.wait_event(wait)`` returns when the next mpv event arrives, or after
+``wait`` seconds if positive and no mpv events arrived. ``wait`` value of 0
+returns immediately (with ``e.event == "none"`` if the queue is empty).
+
+``mp.dispatch_event(e)`` calls back the handlers registered for ``e.event``,
+if there are such (event handlers, property observers, script messages, etc).
+
+``mp.process_timers()`` calls back the already-added, non-canceled due timers,
+and returns the duration in ms till the next due timer (possibly 0), or -1 if
+there are no pending timers. Must not be called recursively.
+
+``mp.notify_idle_observers()`` calls back the idle observers, which we do when
+we're about to sleep (wait != 0), but the observers may add timers or take
+non-negligible duration to complete, so we re-calculate ``wait`` afterwards.
+
+``mp.peek_timers_wait()`` returns the same values as ``mp.process_timers()``
+but without doing anything. Invalid result if called from a timer callback.
+
+Note: ``exit()`` is also registered for the ``shutdown`` event, and its
+implementation is a simple ``mp.keep_running = false``.