Installation
npm install esvm
What to do
ESVM is a virtual machine used to run async/sync program by ECMAScript engine. It provides RPC, Statement and Scope to help to design a execution tree. With ESVM you can easily define statement using the provided template and fetch response from remote with RPC module.
How to use
ESVM
Life Cycle of ESVM
bootstrap
- vm start.load program
- load the defined statement into vm.program run
- run the statement.halt
- vm stops if program end or meets error.
ESVM will be blocked and stop running in several circumstances. The block status can be resumed and make the vm continue to run from the last stop position.
Quick Example
const {ESVM} = require('esvm') // Get vm instance.const vk = new ESVM(); // Define a simple statement.const program = new Statement();program.execute = function* (vm) { yield 'hello';}; // Load the statement into vm.vk.$loadProgram(program); // Run the statement.// VM will halt when execution completed.vk.$launch();
statement
In ESVM, we define a statement template and it can be easily used to implement more complicated statement.
User can define their own statement class by inheriting from Statement
class and then override the constructor
、execute
function.
Example
const {Statement} = require('esvm'); // Define a simple statement.const program = new Statement(); // Implement execute function.program.execute = function* (vm) { yield [statement_1]; yield [statement_2]; ... yield [statement_n];};
rpc
ESVM can send message to remote and get response synchronouslys or asynchronously.
fetch()
is called to start a RPC request, then an event named fetch
will be emmited,
vm will be blocked and wait for response from remote.
Response is in a format like {ret, err} and we can simplely set the value through rpc.setRet(val)
& rpc.setDate(val)
Default Response
{ret: null, err: null}
Async Call
Pass a process
function to async(), and the function will be wrapped with a promise
by async() implementation. Promise can be returned from process
function, and it will
be executed after the previous promise.
rpc.async(vm => { // Can rpc.setRet & setError in async(). // Use vm to access vm-instance of the rpc anywhere. // Some code here ... return new Promise((resolve,reject) => { // Some code ... });});