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JavaScript Duff's Device 达夫设备
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/** | |
* 1. Original JS Implementation by Jeff Greenberg 2/2001 - http://home.earthlink.net/~kendrasg/info/js_opt/ | |
* 2. (fast duff's device) from an anonymous donor to Jeff Greenberg's site | |
* 3. (faster duff's defice) by Andrew King 8/2002 for WebSiteOptimization.com | |
* 4. bug fix (for iterations<8) by Andrew B. King April 12, 2003 | |
*/ | |
function duffsDevice (iterations) { | |
var testVal = 0, | |
n = iterations % 8; | |
if (n > 0) { | |
do { | |
testVal++; | |
} | |
while (--n); // n must be greater than 0 here | |
} | |
n = parseInt(iterations / 8, 10); | |
if (n > 0) { // if iterations < 8 an infinite loop, added for safety in second printing | |
do { | |
testVal++; | |
testVal++; | |
testVal++; | |
testVal++; | |
testVal++; | |
testVal++; | |
testVal++; | |
testVal++; | |
} | |
while (--n); // n must be greater than 0 here also | |
} | |
} |
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