├── LICENSE
├── README.md
└── gameLoop.js


/LICENSE:
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 1 | The MIT License (MIT)
 2 | 
 3 | Copyright (c) 2014 Alex Bennett // timetocode
 4 | 
 5 | Permission is hereby granted, free of charge, to any person obtaining a copy
 6 | of this software and associated documentation files (the "Software"), to deal
 7 | in the Software without restriction, including without limitation the rights
 8 | to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 9 | copies of the Software, and to permit persons to whom the Software is
10 | furnished to do so, subject to the following conditions:
11 | 
12 | The above copyright notice and this permission notice shall be included in all
13 | copies or substantial portions of the Software.
14 | 
15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
18 | AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 | LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 | OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 | SOFTWARE.
22 | 


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/README.md:
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 1 | Edit: 2018
 2 | ==============
 3 | JavaScript timers have improved quite a bit since this repo was created in 2014. The following code can test this:
 4 | ```js
 5 | const hrtimeMs = function() {
 6 |     let time = process.hrtime()
 7 |     return time[0] * 1000 + time[1] / 1000000
 8 | }
 9 | 
10 | const TICK_RATE = 20
11 | let tick = 0
12 | let previous = hrtimeMs()
13 | let tickLengthMs = 1000 / TICK_RATE
14 | 
15 | const loop = () => {
16 |     setTimeout(loop, tickLengthMs)
17 |     let now = hrtimeMs()
18 |     let delta = (now - previous) / 1000
19 |     console.log('delta', delta)
20 |     // game.update(delta, tick) // game logic would go here
21 |     previous = now
22 |     tick++
23 | }
24 | 
25 | loop() // starts the loop
26 | ```
27 | Delta here is in units of seconds (not milliseconds, like it was in the original). The perfect delta at this TICK_RATE would be 0.050000000000. A delta of 0.051 is off by 1 millisecond. If running this code produces satisfactory accuracy on the target machine, then it may be a superior option to the node-game-loop.
28 | 
29 | 
30 | node-game-loop (original readme)
31 | ==============
32 | 
33 | A game loop in node.js capable of accurate frame rates. 
34 | 
35 | This is an alternative to setTimeout/setInterval loops which are accurate to within 16 ms.
36 | 
37 | This is also an alternative to a pure setImmediate loop which is nice and accurate, but will use 100% CPU (well, 100% of one thread) even while idle.
38 | 
39 | 


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/gameLoop.js:
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 1 | /**
 2 | Length of a tick in milliseconds. The denominator is your desired framerate.
 3 | e.g. 1000 / 20 = 20 fps,  1000 / 60 = 60 fps
 4 | */
 5 | var tickLengthMs = 1000 / 20
 6 | 
 7 | /* gameLoop related variables */
 8 | // timestamp of each loop
 9 | var previousTick = Date.now()
10 | // number of times gameLoop gets called
11 | var actualTicks = 0
12 | 
13 | var gameLoop = function () {
14 |   var now = Date.now()
15 | 
16 |   actualTicks++
17 |   if (previousTick + tickLengthMs <= now) {
18 |     var delta = (now - previousTick) / 1000
19 |     previousTick = now
20 | 
21 |     update(delta)
22 | 
23 |     console.log('delta', delta, '(target: ' + tickLengthMs +' ms)', 'node ticks', actualTicks)
24 |     actualTicks = 0
25 |   }
26 | 
27 |   if (Date.now() - previousTick < tickLengthMs - 16) {
28 |     setTimeout(gameLoop)
29 |   } else {
30 |     setImmediate(gameLoop)
31 |   }
32 | }
33 | 
34 | 
35 | /**
36 | Update is normally where all of the logic would go. In this case we simply call
37 | a function that takes 10 milliseconds to complete thus simulating that our game
38 | had a very busy time.
39 | */
40 | var update = function(delta) {
41 |   aVerySlowFunction(10)
42 | }
43 | 
44 | /**
45 | A function that wastes time, and occupies 100% CPU while doing so.
46 | Suggested use: simulating that a complex calculation took time to complete.
47 | */
48 | var aVerySlowFunction = function(milliseconds) {
49 |   // waste time
50 |   var start = Date.now()
51 |   while (Date.now() < start + milliseconds) { }  
52 | }
53 | 
54 | // begin the loop !
55 | gameLoop()
56 | 


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