Continuum is a JavaScript virtual machine built in JavaScript. It assembles bytecode from sourcecode and executes it an ES6 runtime environment. The code of the VM is written in ES3 level JavaScript, which means it can run in browsers as old as IE6. (though currently it's only been tested in IE9+ and there's probably some kinks to work out in older IE's).
ES6 is still an unfinished specification and is still a moving target
Continuum probably works in every modern engine, but has not been tested.
Currently known to work in:
Will soon work in:
In the browser, use the combined continuum.js or continuum.min.js. In node
npm install continuum
In the browser an object named continuum is added to the window, or in node it's the object returned by require('continuum').
Usage of continuum is quite simple and can basically be treated like using eval in iframe or node's vm.runInContext. Supply the code, get the result. In ES6 a "Realm" is basically the container for a context. A Realm has a 'global' property which is its global object, and a number of properties that specific to each Realm instance, such as the list of builtins like Array, Function, Object, etc.
var realm = continuum.createRealm();
var $array = realm.evaluate('[5, 10, 15, 20]');
// you can use the ES internal functions to directly interact with objects
console.log($array.Get(0)) // 5
console.log($array.Get('map')) // $Function object
// these two lines have the same result
var $Function = realm.evaluate('Function');
var $Function = realm.global.Get('Function');
// if your code uses the module system then it must be run asynchronously
realm.evaluateAsync('module F = "@function"; F', function(result){
console.log(result) // $Module { Function, call, apply, bind }
});
module std = '@std' or import call from '@function'A Realm is the main thing you interact with. Each realm has a global object with a unique set of builtin globals. A realm is roughly equivalent to an iframe or a node vm context.
A realm is an Event Emitter and events can be listened to by using realm.on('event', callback). There's also realm.off to remove listeners and realm.once to only get a single event notification.
The following events are emitted by the VM to indicate changes to the state of execution and provide access to information about related objects.
debugger statement is encountered. A function which will resume execution is passed to the callback, and is also available as realm.resume.The following events are emitted by functions from inside the VM to simulate things like input/output and require some implementation on your part to do anything useful.
A Renderer is a visitor used to introspect VM objects and values.
...TODO docs...
An Assembler is used to convert AST into bytecode and static script information.
...TODO docs...
A Script object contains all the static information about a chunk of code: the given options, original source, AST, bytecode, and the compiled thunk that executes the bytecode. Scripts don't contain runtime information so they are portable between realms and can be executed multiple times. When using realm.evaluate or realm.evaluateAsync with a Script, it can be executed directly without compiling again.
...TODO docs...
A Code object contains the compiled bytecode of a Script. It also contains most of the static semantics derived from the source such as bound names, declarations, imports/exports, etc. In the short term future it is planned for Code objects to be serializable to a portable form such that code can be compiled once and then redistributed and executed in this form.
...TODO docs...
All of the higher level functions like DefineOwnProperty, GetOwnProperty, GetP, Enumerate, Call, etc. have many semantics in them that are hard to replicate if you try to replace those functions wholesale with your own implementation. Below these specification functions, continuum uses a simple API that all Object property access and execution eventually goes through. A call to obj.GetOwnProperty will ultimately result in calls to obj.describe(key), obj.set(key, value), and obj.update(key, attribute). These low level functions are responsible for the actual storage and retrieval of the data, once all the preprocessing has been completed by the runtime. To make an exotic object, you can use Continuum's API to make an object with custom callbacks for these low levels functions, making it easy to override and extend.
Below is all most of the functions you can override, and their default implementation. A customized object could either skip some/most of these, could implement completely custom behavior, or could simply augment the normal functionality with some slightly altered behavior
var $MyObjectType = continuum.createExotic('Object', [
// delete a property
function remove(key){
return this.properties.remove(key);
},
function describe(key){
// properties are stored as arrays with 3 fields [key, value, attributes]
// describe is a request for one of these property arrays
return this.properties.getProperty(key);
},
function define(key, value, attrs){
// define sets both the value and the attributes at the same time
return this.properties.set(key, value, attrs);
},
function has(key){
// hasOwnProperty
return this.properties.has(key);
},
function each(callback){
// `each` is the only way the API exposes to get a list of all the properties
this.properties.forEach(callback, this);
},
function get(key){
// retrieve value
return this.properties.get(key);
},
function set(key, value){
// store value, using default attributes if property is new
return this.properties.set(key, value);
},
function query(key){
// retrieve attributes
return this.properties.getAttribute(key);
},
function update(key, attr){
// store attributes
return this.properties.setAttribute(key, attr);
}
]);
FAQs
A JavaScript (ES6) bytecode virtual machine written in JavaScript
The npm package continuum receives a total of 1 weekly downloads. As such, continuum popularity was classified as not popular.
We found that continuum demonstrated a not healthy version release cadence and project activity because the last version was released a year ago. It has 1 open source maintainer collaborating on the project.
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