custom.fn.js

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);


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
//     }
// );

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


var getAbsoluteUrl = (function() {
	var a;

	return function(url) {
		if(!a) a = document.createElement('a');
		a.href = url;

		return a.href;
	};
})();

// Usage
// getAbsoluteUrl('/something'); // https://davidwalsh.name/something


var sheet = (function() {
	// Create the <style> tag
	var style = document.createElement('style');

	// Add a media (and/or media query) here if you'd like!
	// style.setAttribute('media', 'screen')
	// style.setAttribute('media', 'only screen and (max-width : 1024px)')

	// WebKit hack :(
	style.appendChild(document.createTextNode(''));

	// Add the <style> element to the page
	document.head.appendChild(style);

	return style.sheet;
})();

// Usage
// sheet.insertRule("header { float: left; opacity: 0.8; }", 1);


// shim layer with setTimeout fallback
window.requestAnimFrame = (function(){
  return  window.requestAnimationFrame       ||
          window.webkitRequestAnimationFrame ||
          window.mozRequestAnimationFrame    ||
          function( callback ){
            window.setTimeout(callback, 1000 / 60);
          };
})();


// usage:
// instead of setInterval(render, 16) ....

(function animloop(){
  requestAnimFrame(animloop);
  render();
})();
// place the rAF *before* the render() to assure as close to
// 60fps with the setTimeout fallback.


function isElementInViewport(el) {

      //special bonus for those using jQuery
      if (typeof jQuery === "function" && el instanceof jQuery) {
          el = el[0];
      }

      var rect = el.getBoundingClientRect();

      var isTotallyVisible = (
          rect.top >= 0 &&
          rect.left >= 0 &&
          rect.bottom <= (window.innerHeight || document.documentElement.clientHeight) && /*or $(window).height() */
          rect.right <= (window.innerWidth || document.documentElement.clientWidth) /*or $(window).width() */
      );

      return {
        'visible': isTotallyVisible,
        'top': rect.top,
        'bottom': rect.bottom,
        'height': Math.round(rect.bottom - rect.top)
      };
  }