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// 1)Debounce
    // The debounce function can be a game-changer when it comes to event-fueled performance.  
    // If you aren't using a debouncing function with a scroll, resize, key* event, you're probably doing it wrong.  
    // Here's a debounce function to keep your code efficient:

    // 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);
    // The debounce function will not allow a callback to be used more than once per given time frame.  
    // This is especially important when assigning a callback function to frequently-firing events.

// 2)Polling
    // With Deferreds
    // The polling function
    function poll(fn, timeout, interval) {
        var dfd = new Deferred();
        var endTime = Number(new Date()) + (timeout || 2000);
        interval = interval || 100;

        (function p() {
                // If the condition is met, we're done! 
                if(fn()) {
                    dfd.resolve();
                }
                // 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 {
                    dfd.reject(new Error('timed out for ' + fn + ': ' + arguments));
                }
        })();

        return dfd.promise;
    }

    // Usage:  ensure element is visible
    poll(function() {
    	return document.getElementById('lightbox').offsetWidth > 0;
    }, 2000, 150);

    //Without Deferreds
    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
        }
    );

//3)Once Function
    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

// 4)Get an Absolute URL with JavaScript
    var getAbsoluteUrl = (function() {
    	var a;

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

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

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

// 5)isNative
    ;(function() {

      // Used to resolve the internal `[[Class]]` of values
      var toString = Object.prototype.toString;
      
      // Used to resolve the decompiled source of functions
      var fnToString = Function.prototype.toString;
      
      // Used to detect host constructors (Safari > 4; really typed array specific)
      var reHostCtor = /^\[object .+?Constructor\]$/;

      // Compile a regexp using a common native method as a template.
      // We chose `Object#toString` because there's a good chance it is not being mucked with.
      var reNative = RegExp('^' +
        // Coerce `Object#toString` to a string
        String(toString)
        // Escape any special regexp characters
        .replace(/[.*+?^${}()|[\]\/\\]/g, '\\$&')
        // Replace mentions of `toString` with `.*?` to keep the template generic.
        // Replace thing like `for ...` to support environments like Rhino which add extra info
        // such as method arity.
        .replace(/toString|(function).*?(?=\\\()| for .+?(?=\\\])/g, '$1.*?') + '$'
      );
      
      function isNative(value) {
        var type = typeof value;
        return type == 'function'
          // Use `Function#toString` to bypass the value's own `toString` method
          // and avoid being faked out.
          ? reNative.test(fnToString.call(value))
          // Fallback to a host object check because some environments will represent
          // things like typed arrays as DOM methods which may not conform to the
          // normal native pattern.
          : (value && type == 'object' && reHostCtor.test(toString.call(value))) || false;
      }
      
      // export however you want
      module.exports = isNative;
    }());

    // Usage
    isNative(alert); // true
    isNative(myCustomFunction); // false

//6)insertRule
    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(".article-block { color:red}", 0);

//7) matchesSelector
    function matchesSelector(el, selector) {
    	var p = Element.prototype;
    	var f = p.matches || p.webkitMatchesSelector || p.mozMatchesSelector || p.msMatchesSelector || function(s) {
    		return [].indexOf.call(document.querySelectorAll(s), this) !== -1;
    	};
    	return f.call(el, selector);
    }

    // Usage
    matchesSelector(document.getElementById('myDiv'), 'div.someSelector[some-attribute=true]')