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    <p>You'll have to use <code>setTimeout</code> or <code>setInterval</code> in your solution, but it will be inaccurate for the following reasons:</p> <ol> <li>Browsers have a minimum timeout, which is NOT 0ms. The cross-browser minimum is somewhere around 14ms.</li> <li>Timers are inexact. They represent queuing time, not execution time. If something else is executing when your timer fires, your code gets pushed to a queue to wait, and may not actually execute until much later.</li> </ol> <p>You're probably going to want to use <code>setTimeout</code> along with manual tracking of the current time (using <code>Date</code>) to step your program. For your case, try something like this:</p> <pre><code>function someAction(delta) { // ... } function beat() { var currentTime = +new Date; var delta = currentTime - pastTime; if (delta &gt; 430) { // 430ms ~ 140bpm pastTime = currentTime; someAction(); } setTimeout(beat, 107); // 4x resolution } var pastTime = +new Date; beat(); </code></pre> <p>This should approximate 140 beats per minute, using a higher resolution to avoid larger delays. This is just a sample though, you'll probably need to work at it more to get it to perform optimally for your application.</p>
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    1. CO(from @gravityboy) Thanks ben that is a great answer. It does a setimeout 4 times then beat() will only call someaction() if it is over the threshold number, correct? What happens if it is called a few milliseconds before the threshold of 430? Then it doesn't get another chance to fire until it waits out the 107 timeout again? What do you think is the smallest number that can be used in the setTimeout?
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    2. CO(from @gravityboy continued) Also what do you think about just having a loop without a setimeout, just using... var currentTime = +new Date; var delta = currentTime - pastTime; and it will run and check delta at whatever speed the computer will allow? Literally hundreds of times then call the function when delta is exceded. Is that a runaway loop? p.s. I thought the = +new Date was a typo but is is not. It displays the date in milliseconds? I can't even find that documented anywhere.
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    3. COYes, you're correct that this could lead to a 100ms delay. This is just a tradeoff in terms of app responsiveness and timer accuracy. If you did `setTimeout` with 0ms, it will execute the fastest the browser allows (~14ms in some), and this will provide the finest resolution, and thus the greatest accuracy. However, this will come at the expense of the rest of your app. For something simple, this should work great, but for complex apps, this might not work so well.
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