Introduction

node-sync is a simple library that allows you to call any asynchronous function in synchronous way. The main benefit is that it uses javascript-native design - Function.prototype.sync function, instead of heavy APIs which you'll need to learn. Also, asynchronous function which was called synchronously through node-sync doesn't blocks the whole process - it blocks only current thread!

It built on node-fibers library as a multithreading solution.

Examples

Simply call asynchronous function synchronously:

``javascript
var Sync = require('sync');

function asyncFunction(a, b, callback) {
process.nextTick(function(){
callback(null, a + b);
})
}

// Run in a fiber
Sync(function(){

// Function.prototype.sync() interface is same as Function.prototype.call() - first argument is 'this' context
var result = asyncFunction.sync(null, 2, 3);
console.log(result); // 5

// Read file synchronously without blocking whole process? no problem
var source = require('fs').readFile.sync(null, __filename);
console.log(String(source)); // prints the source of this example itself
})
`

It throws exceptions!

`javascript
var Sync = require('sync');

function asyncFunction(a, b, callback) {
process.nextTick(function(){
callback('something went wrong');
})
}

// Run in a fiber
Sync(function(){

try {
var result = asyncFunction.sync(null, 2, 3);
}
catch (e) {
console.error(e); // something went wrong
}
})

// Or simply specify callback function for Sync fiber
// handy when you use Sync in asynchronous environment
Sync(function(){

// The result will be passed to a Sync callback
var result = asyncFunction.sync(null, 2, 3);
return result;

}, function(err, result){ // <-- standard callback

if (err) console.error(err); // something went wrong

// The result which was returned from Sync body function
console.log(result);
})
`

Transparent integration

`javascript
var Sync = require('sync');

var MyNewFunctionThatUsesFibers = function(a, b) { // <-- no callback here

// we can use yield here
// yield();

// or throw an exception!
// throw new Error('something went wrong');

// or even sleep
// Sync.sleep(200);

// or turn fs.readFile to non-blocking synchronous function
// var source = require('fs').readFile.sync(null, __filename)

return a + b; // just return a value

}.async() // <-- here we make this function friendly with async environment

// Classic asynchronous nodejs environment
var MyOldFashoinAppFunction = function() {

// We just use our MyNewFunctionThatUsesFibers normally, in a callback-driven way
MyNewFunctionThatUsesFibers(2, 3, function(err, result){

// If MyNewFunctionThatUsesFibers will throw an exception, it will go here
if (err) return console.error(err);

// 'return' value of MyNewFunctionThatUsesFibers
console.log(result); // 5
})
}

// From fiber environment
Sync(function(){

// Run MyNewFunctionThatUsesFibers synchronously
var result = MyNewFunctionThatUsesFibers(2, 3);
console.log(result); // 5

// Or use sync() for it (same behavior)
var result = MyNewFunctionThatUsesFibers.sync(null, 2, 3);
console.log(result); // 5
})
`

Parallel execution:

`javascript
var Sync = require('sync'),
Future = Sync.Future();

// Run in a fiber
Sync(function(){
try {
// Three function calls in parallel
var foo = asyncFunction.future(null, 2, 3);
var bar = asyncFunction.future(null, 5, 5);
var baz = asyncFunction.future(null, 10, 10);

// We are immediately here, no blocking

// foo, bar, baz - our tickets to the future!
console.log(foo); // { [Function: Future] result: [Getter], error: [Getter] }

// Get the results
// (when you touch 'result' getter, it blocks until result would be returned)
console.log(foo.result, bar.result, baz.result); // 5 10 20

// Or you can straightly use Sync.Future without wrapper
// This call doesn't blocks
asyncFunction(2, 3, foo = Future());

// foo is a ticket
console.log(foo); // { [Function: Future] result: [Getter], error: [Getter] }

// Wait for the result
console.log(foo.result); // 5
}
catch (e) {
// If some of async functions returned an error to a callback
// it will be thrown as exception
console.error(e);
}
})
`

Timeouts support

`javascript
var Sync = require('sync'),
Future = Sync.Future;

function asyncFunction(a, b, callback) {
setTimeout(function(){
callback(null, a + b);
}, 1000)
}

// Run in a fiber
Sync(function(){

// asyncFunction returns the result after 1000 ms
var foo = asyncFunction.future(null, 2, 3);
// but we can wait only 500ms!
foo.timeout = 500;

try {
var result = foo.result;
}
catch (e) {
console.error(e); // Future function timed out at 500 ms
}

// Same example with straight future function
asyncFunction(2, 3, foo = new Future(500));

try {
var result = foo.result;
}
catch (e) {
console.error(e); // Future function timed out at 500 ms
}
})
`

How to address non-uniform callbacks


Sometimes third-party libraries are not following convention and passing multiple result parameters to the callback, e.g. callback(err, recordsets, returnValue). In this situation, node-sync will simply return array of values instead of value.

`javascript
// Asynchronous which returns multiple arguments to a callback and returning a value synchronously
function asyncFunctionReturningMultipleArguments(callback) {
process.nextTick(function(){
callback(null, 2, 3);
})
}

Sync(function(){
var result = asyncFunctionReturningMultipleArguments.sync();
assert.equal(result, [2, 3]);
})
`

See more examples in examples directory.

Installation

install

`bash
$ npm install sync
`
and then

`bash
$ node your_file_using_sync.js
``