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Useful JS Helper Functions
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// Try with scroll, resize, key up/down/etc | |
// 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. | |
function debounce(func, wait, immediate) { | |
var timeout; | |
return function() { | |
var context = this, args = arguments; | |
var later = function() { | |
timeout = null; | |
if (!immediate) func.apply(context, args); | |
}; | |
var callNow = immediate && !timeout; | |
clearTimeout(timeout); | |
timeout = setTimeout(later, wait); | |
if (callNow) func.apply(context, args); | |
}; | |
}; | |
// Usage | |
var myEfficientFn = debounce(function() { | |
// All the taxing stuff you do | |
}, 250); | |
window.addEventListener('resize', myEfficientFn); |
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// function can only fire once | |
function once(fn, context) { | |
var result; | |
return function() { | |
if(fn) { | |
result = fn.apply(context || this, arguments); | |
fn = null; | |
} | |
return result; | |
}; | |
} | |
// Usage | |
var canOnlyFireOnce = once(function() { | |
console.log('Fired!'); | |
}); | |
canOnlyFireOnce(); // "Fired!" | |
canOnlyFireOnce(); // nada |
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// Get absolute URL | |
var getAbsoluteUrl = (function() { | |
var a; | |
return function(url) { | |
if(!a) a = document.createElement('a'); | |
a.href = url; | |
return a.href; | |
}; | |
})(); | |
// Usage | |
getAbsoluteUrl('/something'); | |
// returns http://andrewpierno.com/something |
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// Check for desired state by polling | |
function poll(fn, callback, errback, timeout, interval) { | |
var endTime = Number(new Date()) + (timeout || 2000); | |
interval = interval || 100; | |
(function p() { | |
// If the condition is met, we're done! | |
if(fn()) { | |
callback(); | |
} | |
// If the condition isn't met but the timeout hasn't elapsed, go again | |
else if (Number(new Date()) < endTime) { | |
setTimeout(p, interval); | |
} | |
// Didn't match and too much time, reject! | |
else { | |
errback(new Error('timed out for ' + fn + ': ' + arguments)); | |
} | |
})(); | |
} | |
// Usage: ensure element is visible | |
poll( | |
function() { | |
return document.getElementById('lightbox').offsetWidth > 0; | |
}, | |
function() { | |
// Done, success callback | |
}, | |
function() { | |
// Error, failure callback | |
} | |
); |
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