Created
May 24, 2016 06:08
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var watch = require('observ/watch') | |
module.exports = function (tempo, listener) { | |
var pos = null | |
var length = 25 | |
var destroyed = false | |
var releases = [] | |
if (typeof tempo === 'function') { | |
releases.push(watch(tempo, setTempo)) | |
} else if (typeof tempo === 'number') { | |
setTempo(tempo) | |
} | |
tick() | |
return function () { | |
destroyed = true | |
while (releases.length) { | |
releases.pop()() | |
} | |
} | |
// scoped | |
function setTempo (value) { | |
length = 60000 / (value * 24) | |
} | |
function tick () { | |
if (destroyed) return false | |
if (!pos) { | |
pos = window.performance.now() | |
} | |
pos += length | |
var diff = pos - window.performance.now() | |
listener() | |
setTimeout(tick, diff) | |
} | |
} |
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