babjatom / chillout

Reduce CPU usage in JavaScript

chillout.js

README (日本語)

Reduce JavaScript CPU usage by asynchronous iteration.

Provides asynchronous iteration functions that have a Promise based interface and it can execute with low CPU usage. Each iteration adds delay if the processing is heavy to maintain the CPU stability. Iterate without delay if processing is fast. Therefore, it will realize friendly processing for your machine. It can execute JavaScript without "Warning: Unresponsive Script" alert in the browser.

You can use it in any JavaScript environment (Browser, Electron, Node.js).

Installation

Available on npm as chillout.

$ npm install chillout --save

This can also be installed with Bower.

$ bower install chillout

var chillout = require('chillout');
chillout.forEach(...)

Object chillout will be defined in the global scope if running in the browser window.

Compatibility

The limiting factor for browser/node support is the use of Promise.
You can use es6-shim or other Promise polyfills.

Benchmarks

Benchmarks the ForStatement and chillout.repeat.

function heavyProcess() {
  for (var i = 0; i < 10000; i++) {
    for (var j = 0; j < 10000; j++) {
      var v = i*j;
    }
  }
}

ForStatement

var time = Date.now();
for (var i = 0; i < 500; i++) {
  heavyProcess();
}
var processingTime = Date.now() - time;
console.log(processingTime);

• Processing time: 51049ms.
• CPU total average: 31.10%

chillout.repeat

var time = Date.now();
chillout.repeat(500, function(i) {
  heavyProcess();
}).then(function() {
  var processingTime = Date.now() - time;
  console.log(processingTime);
});

• Processing time: 59769ms.
• CPU total average: 22.76%

Benchmark Result

	ForStatement	chillout.repeat
Processing time	51049ms.	59769ms.
CPU total average	31.10%	22.76%

You can confirm that chillout.repeat is running on a more low CPU usage than ForStatement.

chillout.js can run JavaScript in a natural speed with low CPU usage, but processing speed will be a bit slow.

One of the most important thing of performance in JavaScript, that is not numeric speed, but is to execute without causing stress to the user experience.

(Benchmarks: Windows8.1 / Intel(R) Atom(TM) CPU Z3740 1.33GHz)

Run Benchmark

You can test benchmark with npm run benchmark.

---

Iteration Functions

forEach

Executes a provided function once per array or object element.
The iteration will break if the callback function returns false, or an error occurs.

• chillout.forEach ( obj, callback [, context ] )
  @param {Array|Object} obj Target array or object.
  @param {Function} callback Function to execute for each element, taking three arguments:

  • value: The current element being processed in the array/object.
  • key: The key of the current element being processed in the array/object.
  • obj: The array/object that forEach is being applied to.

  @param {Object} [context] Value to use as this when executing callback.
  @return {Promise} Return new Promise.

Example of array iteration:

var sum = 0;
chillout.forEach([1, 2, 3], function(value, i) {
  sum += value;
}).then(function() {
  console.log(sum); // 6
});

Example of object iteration:

var result = '';
chillout.forEach({ a: 1, b: 2, c: 3 }, function(value, key) {
  result += key + value;
}).then(function() {
  console.log(result); // 'a1b2c3'
});

repeat

Executes a provided function the specified number times.
The iteration will break if the callback function returns false, or an error occurs.

• chillout.repeat ( count, callback [, context ] )
  @param {number|Object} count The number of times or object for execute the function.
  Following parameters are available if specify object:

  • start: The number of start.
  • step: The number of step.
  • end: The number of end.

  @param {Function} callback Function to execute for each times, taking one argument:

  • i: The current number.

  @param {Object} [context] Value to use as this when executing callback.
  @return {Promise} Return new Promise.

Example of specify number:

chillout.repeat(5, function(i) {
  console.log(i);
}).then(function() {
  console.log('end');
});
// 0
// 1
// 2
// 3
// 4
// end

Example of specify object:

chillout.repeat({ start: 10, step: 2, end: 20 }, function(i) {
  console.log(i);
}).then(function() {
  console.log('end');
});
// 10
// 12
// 14
// 16
// 18
// end

till

Executes a provided function until the callback returns false, or an error occurs.

• chillout.till ( callback [, context ] )
  @param {Function} callback The function that is executed for each iteration.
  @param {Object} [context] Value to use as this when executing callback.
  @return {Promise} Return new Promise.

var i = 0;
chillout.till(function() {
  console.log(i);
  i++;
  if (i === 5) {
    return false; // stop iteration
  }
}).then(function() {
  console.log('end');
});
// 0
// 1
// 2
// 3
// 4
// end

forOf

Iterates the iterable objects, similar to the for-of statement.
Executes a provided function once per element.
The iteration will break if the callback function returns false, or an error occurs.

• chillout.forOf ( iterable, callback [, context ] )
  @param {Array|string|Object} iterable Target iterable objects.
  @param {Function} callback Function to execute for each element, taking one argument:

  • value: A value of a property on each iteration.

  @param {Object} [context] Value to use as this when executing callback.
  @return {Promise} Return new Promise.

Example of iterate array:

chillout.forOf([1, 2, 3], function(value) {
  console.log(value);
}).then(function() {
  console.log('end');
});
// 1
// 2
// 3
// end

Example of iterate string:

chillout.forOf('abc', function(value) {
  console.log(value);
}).then(function() {
  console.log('end');
});
// a
// b
// c
// end

Comparison Table

You can reduce the CPU load by changing your JavaScript iteration to the chillout iteration.

Examples:

JavaScript Statement	chillout
[1, 2, 3].forEach(function(v, i) {})	chillout.forEach([1, 2, 3], function(v, i) {})
for (i = 0; i < 5; i++) {}	chillout.repeat(5, function(i) {})
for (i = 10; i < 20; i += 2) {}	chillout.repeat({ start: 10, step: 2, end: 20 }, function(i) {})
while (true) {}	chillout.till(function() {})
while (cond()) {}	chillout.till(function() {   if (!cond()) return false; })
for (value of [1, 2, 3]) {}	chillout.forOf([1, 2, 3], function(value) {})

Contributing

I'm waiting for your pull requests and issues. Don't forget to execute npm test before requesting. Accepted only requests without errors.

License

MIT