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![1. Define function for Test casesvar test = function(name, fun, times) {// validate timesif(times < 1) throw 'Invalid times';// initvartimers = [new Date()], count = 0, total = 0;// run test casewhile(count++ < times) { fun();timers[count] = new Date();}// output resultdocument.write("<p>Result for " + name + ":<br/>");for(vari = 1, interval = 0; i <= times; i++) {document.write(i + " - " + (interval = timers[i] - timers[i - 1]) + "ms<br/>");total += interval;}document.write("Average: " + (total / times) + "ms</p>");};](https://image.slidesharecdn.com/javascriptloop-100511012048-phpapp01/85/JavaScript-Loop-Optimization-of-Weak-Typing-9-320.jpg)
![1. Define function for Test casesvar test = function(name, fun, times) {// validate timesif(times < 1) throw 'Invalid times';// initvartimers = [new Date()], count = 0, total = 0;// run test casewhile(count++ < times) { fun();timers[count] = new Date();}// output resultdocument.write("<p>Result for " + name + ":<br/>");for(vari = 1, interval = 0; i <= times; i++) {document.write(i + " - " + (interval = timers[i] - timers[i - 1]) + "ms<br/>");total += interval;}document.write("Average: " + (total / times) + "ms</p>");};](https://image.slidesharecdn.com/javascriptloop-100511012048-phpapp01/75/JavaScript-Loop-Optimization-of-Weak-Typing-9-2048.jpg)
Uploaded byJanlay Wu
JavaScript Loop: Optimization of Weak Typing
This document discusses JavaScript loop optimization and the difference in performance between i++ and i-- loops. It shows that i++ and i-- have similar performance in modern browsers. To better measure the performance, it defines test functions that run the loops 10,000 times with 1,000,000 iterations each. The results show minor differences between browsers but no clear winner between i++ and i--. It also discusses the differences between strong/weak and static/dynamic typing in JavaScript compared to languages like C/Java.
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Similar to JavaScript Loop: Optimization of Weak Typing
JavaScript Loop: Optimization of Weak Typing
- 1. JavaScript LoopOptimization ofweak typingtaibo@alipay.com
- 2. AboutJanlay Wux涂料Gtalk: janlay@gmail.comQQ:629489Twitter: @janlayBlog: janlay.com5dmedia.comSunSourcing.comaabase.comRe1001.comAlipay.com
- 3. i++ vs i--for(vari = 0, stub = 0; i < 100000; i++) { stub++;}for(vari = 100000, stub = 0; i > 0; i--) {stub++; }
- 4.
- 5. Run the codei--IE8: 41-55 msChrome 5: 3-7 msFirefox 3: 0-2 msOpera 10: 0-1 msi++IE 8: 43-48 msChrome 5: 1-5 msFirefox 3: 0-2 msOpera 10: 0-1 ms
- 6.
- 7. Why i–- isnot significantly faster?Too Young: No warming upToo Simple: Only one statementAnd, depends on JavaScript Compiler
- 8. Make them morecomplex
- 9. 1. Define functionfor Test casesvar test = function(name, fun, times) {// validate timesif(times < 1) throw 'Invalid times';// initvartimers = [new Date()], count = 0, total = 0;// run test casewhile(count++ < times) { fun();timers[count] = new Date();}// output resultdocument.write("<p>Result for " + name + ":<br/>");for(vari = 1, interval = 0; i <= times; i++) {document.write(i + " - " + (interval = timers[i] - timers[i - 1]) + "ms<br/>");total += interval;}document.write("Average: " + (total / times) + "ms</p>");};
- 10. 2. Use itvarstub = 0; test('i--', function() { for(var i = 100000; i > 0; i--) { stub++; // access variable out of closure } }, 10); test('i++', function() { for(var i = 0; i < 100000; i++) { stub++; } }, 10);
- 11.
- 12. So, we goti--IE8: 25.4 msChrome 5: 1.8 msFirefox 3: 0.8 msOpera 10: 2.2 msi++IE 8: 27.8 msChrome 5: 0.8 msFirefox 3: 1.0 msOpera 10: 2.0 ms
- 13. Just ignore thedifferences1.0 / 100,000 / 1,000 => 1/100,000,000 (s)
- 14.
- 15. Typing!JavaScript is quitedifferent from Java/C
- 16. JavaScript is quitedifferent from Java/CStrong Typing vs Weak TypingStatic Typing vs Dynamic Typing
- 17. Strong Typing vsWeak TypingC: short, int, long, float…1.0fvs1++ designed for CPU instruction INC++ => INC, -- => DEC> 0 => JNZ (only i--, non-float)< 1 => SUBB, JNCJavaScript: Number1.0 ~ ’1’++ inherits from C-style languages++ equals +1, mostly
- 18. Static Typing vsDynamicTypingC: types determined in compile timeMay be benefit for optimizationJIT on VM(msvcrt, JVM, .NET…)JavaScript: types determined in run timeBasedon VM, cannot use CPU instructions directly
- 19. Finally…Consider business logici--:order-independentFocus on the most important partyou know it
- 20.