Created
May 29, 2015 08:25
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throttle and debounce functions extracted from underscore.js
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(function(){ | |
var _ = {}; | |
_.now = Date.now || function(){ | |
return new Date().getTime(); | |
}; | |
// Returns a function, that, when invoked, will only be triggered at most once | |
// during a given window of time. Normally, the throttled function will run | |
// as much as it can, without ever going more than once per `wait` duration; | |
// but if you'd like to disable the execution on the leading edge, pass | |
// `{leading: false}`. To disable execution on the trailing edge, ditto. | |
_.throttle = function(func, wait, options) { | |
var context, args, result; | |
var timeout = null; | |
var previous = 0; | |
if (!options) options = {}; | |
var later = function() { | |
previous = options.leading === false ? 0 : _.now(); | |
timeout = null; | |
result = func.apply(context, args); | |
if (!timeout) context = args = null; | |
}; | |
return function() { | |
var now = _.now(); | |
if (!previous && options.leading === false) previous = now; | |
var remaining = wait - (now - previous); | |
context = this; | |
args = arguments; | |
if (remaining <= 0 || remaining > wait) { | |
if (timeout) { | |
clearTimeout(timeout); | |
timeout = null; | |
} | |
previous = now; | |
result = func.apply(context, args); | |
if (!timeout) context = args = null; | |
} else if (!timeout && options.trailing !== false) { | |
timeout = setTimeout(later, remaining); | |
} | |
return result; | |
}; | |
}; | |
// Returns a function, that, as long as it continues to be invoked, will not | |
// be triggered. The function will be called after it stops being called for | |
// N milliseconds. If `immediate` is passed, trigger the function on the | |
// leading edge, instead of the trailing. | |
_.debounce = function(func, wait, immediate) { | |
var timeout, args, context, timestamp, result; | |
var later = function() { | |
var last = _.now() - timestamp; | |
if (last < wait && last >= 0) { | |
timeout = setTimeout(later, wait - last); | |
} else { | |
timeout = null; | |
if (!immediate) { | |
result = func.apply(context, args); | |
if (!timeout) context = args = null; | |
} | |
} | |
}; | |
return function() { | |
context = this; | |
args = arguments; | |
timestamp = _.now(); | |
var callNow = immediate && !timeout; | |
if (!timeout) timeout = setTimeout(later, wait); | |
if (callNow) { | |
result = func.apply(context, args); | |
context = args = null; | |
} | |
return result; | |
}; | |
}; | |
return { | |
throttle : _.throttle, | |
debounce : _.debounce | |
}; | |
}()); |
Just what I was looking for, only needed throttle.
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Thanks heaps for this! Saved me from having to include all of Underscore.js in my project just to use
_.throttle
. 😄