yaku

What is yaku?

Yaku is a lightweight and fast Promise library that is fully compatible with ES6 Promises. It aims to provide better performance and smaller size compared to native Promises and other Promise libraries.

What are yaku's main functionalities?

Basic Promise Usage

This demonstrates the basic usage of Yaku to create a new Promise and handle its resolution.

const Yaku = require('yaku');

const promise = new Yaku((resolve, reject) => {
  setTimeout(() => resolve('Hello, Yaku!'), 1000);
});

promise.then(value => console.log(value));

Chaining Promises

This demonstrates how to chain multiple `then` calls to handle the resolved value step by step.

const Yaku = require('yaku');

const promise = new Yaku((resolve, reject) => {
  setTimeout(() => resolve(1), 1000);
});

promise
  .then(value => value + 1)
  .then(value => value * 2)
  .then(value => console.log(value));

Error Handling

This demonstrates how to handle errors in Yaku Promises using the `catch` method.

const Yaku = require('yaku');

const promise = new Yaku((resolve, reject) => {
  setTimeout(() => reject(new Error('Something went wrong')), 1000);
});

promise
  .then(value => console.log(value))
  .catch(error => console.error(error.message));

Promise.all

This demonstrates how to use `Yaku.all` to wait for multiple Promises to resolve.

const Yaku = require('yaku');

const promise1 = Yaku.resolve(1);
const promise2 = Yaku.resolve(2);
const promise3 = Yaku.resolve(3);

Yaku.all([promise1, promise2, promise3])
  .then(values => console.log(values));

Other packages similar to yaku

bluebird

Bluebird is a fully featured Promise library with a focus on performance and additional features not found in native Promises. It offers more utility methods and better error handling compared to Yaku, but it is larger in size.

q

Q is another Promise library that provides a lot of additional functionality such as deferred objects and more advanced control flow. It is more feature-rich compared to Yaku but also comes with a larger footprint.

when

When is a lightweight Promise library that focuses on performance and small size, similar to Yaku. It provides a few more utilities for working with Promises but is generally comparable in terms of performance and size.

README

Overview

Yaku is full compatible with ES6's native Promise, but much faster, and more error friendly. If you want to learn how Promise works, read the minimum implementation docs/minPromiseA+.coffee. Without comments, it is only 80 lines of code (gzipped size is 0.5KB). It only implements the constructor and then. It passed all the tests of promises-aplus-tests.

I am not an optimization freak, I try to keep the source code readable and maintainable. Premature optimization is the root of all evil. I write this lib to research one of my data structure ideas: docs/lazyTree.md.

Features

• The minified file is only 3.2KB (1.5KB gzipped) (Bluebird / 73KB, ES6-promise / 18KB)
• Better "possibly unhandled rejection" and "long stack trace" than Bluebird
• Much better performance than the native Promise
• 100% compliant with Promises/A+ specs and ES6
• Designed to work on IE5+ and other major browsers
• Well commented source code with every Promises/A+ spec

Quick Start

Node.js

npm install yaku

Then:

var Promise = require('yaku');

Browser

Use something like Browserify or Webpack, or download the yaku.js file from release page. It supports both AMD, CMD and CommonJS. Raw usage without AMD, CMD or CommonJS:

<script type="text/javascript" src ="yaku.js"></script>
<script>
    // Yaku will be assigned to `window.Yaku`.
    var Promise = Yaku;
</script>

Change Log

docs/changelog.md

Compare to Other Promise Libs

These comparisons only reflect some limited truth, no one is better than all others on all aspects. For more details see the benchmark/readme.md. There are tons of Promises/A+ implementations, you can see them here. Only some of the famous ones were tested.

Name	1ms async task / mem	sync task / mem	Helpers	file size
Yaku	257ms / 110MB	126ms / 80MB	+++	3.2KB
Bluebird v2.9	249ms / 102MB	155ms / 80MB	+++++++	73KB
ES6-promise v2.3	427ms / 120MB	92ms / 78MB	+	18KB
native iojs v1.8	789ms / 189MB	605ms / 147MB	+	0KB
q v1.3	2648ms / 646MB	2373ms / 580MB	+++	24K

• Helpers: extra methods that help with your promise programming, such as async flow control helpers, debug helpers. For more details: docs/debugHelperComparison.md.
• 1ms async task: npm run no -- benchmark, the smaller the better.
• sync task: npm run no -- benchmark --sync, the smaller the better.

FAQ

• catch on old brwoser (IE7, IE8 etc)?

  In ECMA-262 spec, catch cannot be used as method name. You have to alias the method name or use something like Promise.resolve()['catch'](function() {}) or Promise.resolve().then(null, function() {}).

• Will Yaku implement done, finally, promisify, etc?

  No. All non-ES6 APIs are only implemented for debugging and testing, which means when you remove Yaku, everything should work well with ES6 native promise. If you need fancy and magic, go for Bluebird.

• Better long stack trace support?

  Latest Node.js and browsers are already support it. If you enabled it, Yaku will take advantage of it without much overhead. Such as this library longjohn for Node.js, or this article for Chrome.

• The name Yaku is weird?

  The name yaku comes from the word 約束(yakusoku) which means promise.

API

• Yaku(executor)

  This class follows the Promises/A+ and ES6 spec with some extra helpers.

  • param: executor { Function }

    Function object with three arguments resolve, reject and the promise itself. The first argument fulfills the promise, the second argument rejects it. We can call these functions, once our operation is completed. The this context of the executor is the promise itself, it can be used to add custom handlers, such as abort or progress helpers.

  • example:

    Here's an abort example.

    var Promise = require('yaku');
    var p = new Promise((resolve, reject) => {
        var tmr = setTimeout(resolve, 3000);
        this.abort = (reason) => {
            clearTimeout(tmr);
            reject(reason);
        };
    });
    
    p.abort(new Error('abort'));
    

  • example:

    Here's a progress example.

    var Promise = require('yaku');
    var p = new Promise((resolve, reject) => {
        var self = this;
        var count = 0;
        var all = 100;
        var tmr = setInterval(() => {
            try {
                self.progress && self.progress(count, all);
            } catch (err) {
                reject(err);
            }
    
            if (count < all)
                count++;
            else {
                resolve();
                clearInterval(tmr);
            }
        }, 1000);
    });
    
    p.progress = (curr, all) => {
        console.log(curr, '/', all);
    };
    

• then(onFulfilled, onRejected)

  Appends fulfillment and rejection handlers to the promise, and returns a new promise resolving to the return value of the called handler.

  • param: onFulfilled { Function }

    Optional. Called when the Promise is resolved.

  • param: onRejected { Function }

    Optional. Called when the Promise is rejected.

  • return: { Yaku }

    It will return a new Yaku which will resolve or reject after

  • example:

    the current Promise.

    var Promise = require('yaku');
    var p = Promise.resolve(10);
    
    p.then((v) => {
        console.log(v);
    });
    

• catch(onRejected)

  The catch() method returns a Promise and deals with rejected cases only. It behaves the same as calling Promise.prototype.then(undefined, onRejected).

  • param: onRejected { Function }

    A Function called when the Promise is rejected. This function has one argument, the rejection reason.

  • return: { Yaku }

    A Promise that deals with rejected cases only.

  • example:

    var Promise = require('yaku');
    var p = Promise.reject(10);
    
    p['catch']((v) => {
        console.log(v);
    });
    

• Yaku.resolve(value)

  The Promise.resolve(value) method returns a Promise object that is resolved with the given value. If the value is a thenable (i.e. has a then method), the returned promise will "follow" that thenable, adopting its eventual state; otherwise the returned promise will be fulfilled with the value.

  • param: value { Any }

    Argument to be resolved by this Promise. Can also be a Promise or a thenable to resolve.

  • return: { Yaku }

  • example:

    var Promise = require('yaku');
    var p = Promise.resolve(10);
    

• Yaku.reject(reason)

  The Promise.reject(reason) method returns a Promise object that is rejected with the given reason.

  • param: reason { Any }

    Reason why this Promise rejected.

  • return: { Yaku }

  • example:

    var Promise = require('yaku');
    var p = Promise.reject(10);
    

• Yaku.race(iterable)

  The Promise.race(iterable) method returns a promise that resolves or rejects as soon as one of the promises in the iterable resolves or rejects, with the value or reason from that promise.

  • param: iterable { iterable }

    An iterable object, such as an Array.

  • return: { Yaku }

    The race function returns a Promise that is settled the same way as the first passed promise to settle. It resolves or rejects, whichever happens first.

  • example:

    var Promise = require('yaku');
    Promise.race([
        123,
        Promise.resolve(0)
    ])
    .then((value) => {
        console.log(value); // => 123
    });
    

• Yaku.all(iterable)

  The Promise.all(iterable) method returns a promise that resolves when all of the promises in the iterable argument have resolved.

  The result is passed as an array of values from all the promises. If something passed in the iterable array is not a promise, it's converted to one by Promise.resolve. If any of the passed in promises rejects, the all Promise immediately rejects with the value of the promise that rejected, discarding all the other promises whether or not they have resolved.

  • param: iterable { iterable }

    An iterable object, such as an Array.

  • return: { Yaku }

  • example:

    var Promise = require('yaku');
    Promise.all([
        123,
        Promise.resolve(0)
    ])
    .then((values) => {
        console.log(values); // => [123, 0]
    });
    

• Yaku.onUnhandledRejection(reason, p)

  Catch all possibly unhandled rejections. If you want to use specific format to display the error stack, overwrite it. If it is set, auto console.error unhandled rejection will be disabed.

  • param: reason { Any }

    The rejection reason.

  • param: p { Yaku }

    The promise that was rejected.

  • example:

    var Promise = require('yaku');
    Promise.onUnhandledRejection = (reason) => {
        console.error(reason);
    };
    
    # The console will log an unhandled rejection error message.
    Promise.reject('my reason');
    
    # The below won't log the unhandled rejection error message.
    Promise.reject('v').catch(() => {});
    

• Yaku.enableLongStackTrace

  It is used to enable the long stack trace. Once it is enabled, it can't be reverted. While it is very helpful in development and testing environments, it is not recommended to use it in production. It will slow down your application and waste your memory.

  • example:

    var Promise = require('yaku');
    Promise.enableLongStackTrace();
    

• Yaku.nextTick

  Only Node has process.nextTick function. For browser there are so many ways to polyfill it. Yaku won't do it for you, instead you can choose what you prefer. For example, this project setImmediate. By default, Yaku will use process.nextTick on Node, setTimeout on browser.

  • type: { Function }

  • example:

    var Promise = require('yaku');
    Promise.nextTick = fn => window.setImmediate(fn);
    

  • example:

    You can even use sync resolution if you really know what you are doing.

    var Promise = require('yaku');
    Promise.nextTick = fn => fn();
    

Utils

To use it you have to require it separately: yutils = require 'yaku/lib/utils'. If you want to use it in the browser, you have to use browserify or webpack.

• async(limit, list, saveResults, progress)

  An throttled version of Promise.all, it runs all the tasks under a concurrent limitation. To run tasks sequentially, use utils.flow.

  • param: limit { Int }

    The max task to run at a time. It's optional. Default is Infinity.

  • param: list { Array | Function }

    If the list is an array, it should be a list of functions or promises, and each function will return a promise. If the list is a function, it should be a iterator that returns a promise, when it returns utils.end, the iteration ends. Of course it can never end.

  • param: saveResults { Boolean }

    Whether to save each promise's result or not. Default is true.

  • param: progress { Function }

    If a task ends, the resolve value will be passed to this function.

  • return: { Promise }

  • example:

    var kit = require('nokit');
    var utils = require('yaku/lib/utils');
    
    var urls = [
     'http://a.com',
     'http://b.com',
     'http://c.com',
     'http://d.com'
    ];
    var tasks = [
     () => kit.request(url[0]),
     () => kit.request(url[1]),
     () => kit.request(url[2]),
     () => kit.request(url[3])
    ];
    
    utils.async(tasks).then(() => kit.log('all done!'));
    
    utils.async(2, tasks).then(() => kit.log('max concurrent limit is 2'));
    
    utils.async(3, () => {
     var url = urls.pop();
     if (url)
         return kit.request(url);
     else
         return utils.end;
    })
    .then(() => kit.log('all done!'));
    

• callbackify(fn, self)

  If a function returns promise, convert it to node callback style function.

  • param: fn { Function }

  • param: self { Any }

    The this to bind to the fn.

  • return: { Function }

• Deferred

  Create a jQuery.Deferred like object.

• end()

  The end symbol.

  • return: { Promise }

    A promise that will end the current pipeline.

• flow(fns)

  Creates a function that is the composition of the provided functions. Besides, it can also accept async function that returns promise. See utils.async, if you need concurrent support.

  • param: fns { Function | Array }

    Functions that return promise or any value. And the array can also contains promises or values other than function. If there's only one argument and it's a function, it will be treated as an iterator, when it returns utils.end, the iteration ends.

  • return: { Function }

    (val) -> Promise A function that will return a promise.

  • example:

    It helps to decouple sequential pipeline code logic.

    var kit = require('nokit');
    var utils = require('yaku/lib/utils');
    
    function createUrl (name) {
    	return "http://test.com/" + name;
    }
    
    function curl (url) {
    	return kit.request(url).then((body) => {
    		kit.log('get');
    		return body;
    	});
    }
    
    function save (str) {
    	kit.outputFile('a.txt', str).then(() => {
    		kit.log('saved');
    	});
    }
    
    var download = utils.flow(createUrl, curl, save);
    # same as "download = utils.flow([createUrl, curl, save])"
    
    download('home');
    

  • example:

    Walk through first link of each page.

    var kit = require('nokit');
    var utils = require('yaku/lib/utils');
    
    var list = [];
    function iter (url) {
    	if (!url) return utils.end;
    
    	return kit.request(url)
    	.then((body) => {
    		list.push(body);
    		var m = body.match(/href="(.+?)"/);
    		if (m) return m[0];
    	});
    }
    
    var walker = utils.flow(iter);
    walker('test.com');
    

• isPromise(obj)

  Check if an object is a promise-like object.

  • param: obj { Any }

  • return: { Boolean }

• promisify(fn, self)

  Convert a node callback style function to a function that returns promise when the last callback is not supplied.

  • param: fn { Function }

  • param: self { Any }

    The this to bind to the fn.

  • return: { Function }

  • example:

    function foo (val, cb) {
    	setTimeout(() => {
    		cb(null, val + 1);
    	});
    }
    
    var bar = utils.promisify(foo);
    
    bar(0).then((val) => {
    	console.log val # output => 1
    });
    
    # It also supports the callback style.
    bar(0, (err, val) => {
    	console.log(val); // output => 1
    });
    

• sleep(time, val)

  Create a promise that will wait for a while before resolution.

  • param: time { Integer }

    The unit is millisecond.

  • param: val { Any }

    What the value this promise will resolve.

  • return: { Promise }

  • example:

    utils.sleep(1000).then(() => console.log('after one second'));
    

• source(executor)

  Create a composable event source function. Promise can't resolve multiple times, this function makes it possible, so that you can easily map, filter and debounce events in a promise way.

  • param: executor { Function }

    (emit) -> It's optional.

  • return: { Function }

    (value) -> The fucntion's members:

    {
    	on: (onEmit, onError) => { /* ... */ },
    
    	// Get current value from it.
    	value: Promise,
    
    	// All the children spawned from current source.
    	children: Array
    }
    

  • example:

    var linear = utils.source();
    
    var x = 0;
    setInterval(() => {
    	linear(x++);
    }, 1000);
    
    // Wait for a moment then emit the value.
    var quad = linear.on(async x => {
    	await utils.sleep(2000);
    	return x * x;
    });
    
    var another = linear.on(x => -x);
    
    quad.on(
    	value => { console.log(value); },
    	reason => { console.error(reason); }
    );
    
    // Dispose a specific source.
    linear.children.splice(linear.children.indexOf(quad));
    
    // Dispose all children.
    linear.children = [];
    

  • example:

    Use it with DOM.

    var filter = fn => v => fn(v) ? v : utils.end();
    
    var keyup = utils.source((emit) => {
    	document.querySelector('input').onkeyup = emit;
    });
    
    var keyupText = keyup.on(e => e.target.value);
    
    // Now we only get the input when the text length is greater than 3.
    var keyupTextGT3 = keyupText.on(filter(text => text.length > 3));
    
    keyupTextGT3(v => console.log(v));
    

  • example:

    Merge two sources into one.

    let one = utils.source(emit => setInterval(emit, 100, 'one'));
    let two = utils.source(emit => setInterval(emit, 200, 'two'));
    let merge = arr => arr.forEach(src => src.on(emit));
    
    let three = merge([one, two]);
    three.on(v => console.log(v));
    

• throw(err)

  Throw an error to break the program.

  • param: err { Any }

  • example:

    Promise.resolve().then(() => {
    	// This error won't be caught by promise.
    	utils.throw('break the program!');
    });
    

Unit Test

This project use promises-aplus-tests to test the compliance of Promises/A+ specification. There are about 900 test cases.

Use npm run no -- test to run the unit test.

Benchmark

Use npm run no -- benchmark to run the benchmark.

Contribute

Other than use gulp, all my projects use nokit to deal with automation. Run npm run no -- -h to print all the tasks that defined in the nofile.coffee. If you installed nokit globally, you can just run no -h without npm run and --.