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@ -0,0 +1,340 @@ |
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It is a well known fact that a fast website is critical towards having high user retention. |
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Google looks favorable upon websites which are well optimized and fast. If you are using |
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a CMS like WordPress or Wix, a lot of optimization is done automatically. If you like to |
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build stuff from scratch like me, there is a ton of work required to optimize a website. |
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This post will cover the 8 things that I did to decrease the load time of this node blog |
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by two seconds. |
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#### After Optimization |
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#### Before Optimization |
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## 1: Optimize Images |
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Since images are the largest portion of a website's size, optimizing and reducing the |
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size of images will greatly decrease load time. In a perfect web development world, everyone would |
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use SVG images which are extremely small and don't need compression. However, since most of us |
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use PNG and JPEG images I wrote a script to automatically optimize images for the web. |
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``` |
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#!/bin/bash |
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# Simple script for optimizing all images for a website |
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# |
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# @author Jeffery Russell 7-19-18 |
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WIDTH="690>" # the ">" tag specifies that images will not get scaled up |
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folders=("./entries" "./img") |
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for folder in "${folders[@]}"; do |
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for f in $(find $folder -name '*.jpg' -or -name '*.JPG'); do |
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convert "$f" -resize $WIDTH "$f" |
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jpegoptim --max=80 --strip-all --preserve --totals --all-progressive "$f" |
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done |
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for f in $(find $folder -name '*.png' -or -name '*.PNG'); do |
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convert "$f" -resize $WIDTH "$f" |
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optipng -o7 -preserve "$f" |
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done |
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done |
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``` |
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When ran, this script will go through the img, and entries folder recursively and optimize all |
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the images in there. If an image is more than 690px wide, it will scale it down to save size. In |
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most cases, it is useless to have images with a width greater than 690 because it will just get |
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scaled by the client's web browser. |
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If you are running a Debian based linux distro, you can download the dependencies for this script with |
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the following commands: |
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``` |
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apt-get install jpegoptim |
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apt-get install optipng |
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``` |
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The goal of this script is to make most of the images under 100kb for the web. It is ok to have |
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a few images above 100k, however, you should really avoid having images above 200kb. |
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## 2: Take advantage of Async calls |
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One of the largest benefits of node is its async abilities where code is executed in a |
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multi-threaded fashion. This can become a callback hell if not handled correctly, but, with |
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good code structure it can become very easy. When code is executed in parallel, you can greatly |
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decrease run time by doing other stuff while waiting on costly file IO or database calls. |
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The problem with async code is that it is hard to coordinate. Node has a lot of ways to handel |
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synchronization, but, I prefer to use [Promises](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Promise) |
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. Here is a simple example where async code can become inefficient. |
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Good Code Async: |
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``` |
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Promise.all([includes.printHeader(), |
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require(file).main(filename, request), |
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includes.printFooter()]).then(function(content) |
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{ |
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res.write(content.join('')); |
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res.end(); |
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}).catch(function(err) |
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{ |
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console.log(err); |
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}); |
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``` |
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Bad Async Code: |
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``` |
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includes.printHeader(res).then(function() |
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{ |
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return require(file).main(res, filename, request); |
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}).then(function() |
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{ |
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return includes.printFooter(res); |
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}).catch(function(err) |
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{ |
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console.log(err); |
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}) |
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``` |
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In the first example three blocks of async code are executed in parallel and in the second example |
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three blocks of async code are executed one after another. Many people may initially do the second |
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option because it may seem like you have to create and render the footer after you render the header |
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and body of the page. |
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A great way to handel async calls is by having most of your methods returning promises which resolve to |
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the HTML or DB information that they produce. When you run Promise.all, it returns an array of the |
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objects which enables you to preserve the order ie header, body, footer. After you do this for all of |
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your code, it creates a "perfect" async tree which actually runs very fast. |
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Another Good Async Example: |
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``` |
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/** |
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* Calls posts and sidebar modules to render blog contents in order |
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* |
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* @param requestURL |
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* @returns {Promise|*} |
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*/ |
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main: function(requestURL) |
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{ |
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return new Promise(function(resolve, reject) |
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{ |
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Promise.all([renderPost(requestURL), |
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require("../sidebar/sidebar.js").main()]).then(function(content) |
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{ |
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resolve(content.join('')); |
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}).catch(function(error) |
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{ |
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reject(error); |
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}) |
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}); |
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} |
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``` |
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## 3: Client Side Caching |
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Client side caching is where the client's web browser stores static content they |
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receive from your website. For example, |
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if a client caches a downloaded css style sheet, they won't have to download it again for the next page |
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they visit on your website with that style sheet. |
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You should cache all images, Javascript and css files since those typically don't change. |
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It is a good idea to set the expiration date of the cache to be something longer than a week, I typically |
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set mine for a month. |
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In order for a web browser to accept and cache files, you must set some tags in the HTTP header of the |
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response which you send to the client. In this header you must specify the content type, some cache variables |
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like its max age. You also must assign a ETag to the header to give the client a way to verify the content |
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of the cache. This enables the client to detect if there was a change to the file. Some people set the ETag |
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equal to the version of the stylesheet or javascript, but, it is far easier to just set it equal to the hash of the |
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file. I use md5 to hash the files since it is fast and I'm not worried about hash collisions for this particular |
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application. |
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You can do this in NGINX if you use it to serve static files, but, you can also do it |
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in Node. |
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#### Caching CSS |
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``` |
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var eTag = crypto.createHash('md5').update(content).digest('hex'); |
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result.writeHead(200, {'Content-Type': 'text/css', 'Cache-Control': |
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'public, max-age=2678400', 'ETag': '"' + eTag + '"', |
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'Vary': 'Accept-Encoding'}); |
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result.write(content); |
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result.end(); |
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``` |
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#### Caching Images |
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``` |
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var eTag = crypto.createHash('md5').update(content).digest('hex'); |
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result.writeHead(200, {'Content-Type': 'image/png', |
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'Cache-Control': 'public, max-age=2678400', |
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'ETag': '"' + eTag + '"'}); |
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result.write(content); |
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result.end(); |
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``` |
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## 4: Server Side Caching |
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Even with the best async server, there are still ways to improve performance. If |
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you cache all the static pages that you generate in a HashMap, you can quickly access |
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it for the next web user without ever having to query the database or read files. |
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``` |
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const cache = require('memory-cache'); |
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var html = cache.get(filename); |
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if(html == null) |
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{ |
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// Generate page contents |
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Promise.all([includes.printHeader(), |
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require(file).main(filename, request), |
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includes.printFooter()]).then(function(content) |
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{ |
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res.write(content.join('')); |
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res.end(); |
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cache.put(filename, content.join('')); |
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}) |
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} |
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else |
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{ |
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res.write(html); |
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res.end(); |
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} |
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``` |
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I found that it is the fastest to cache everything from static html pages, CSS, JavaScript, |
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and Images. For a larger site this may consume a boat load of ram, but, storing images in a HashMap |
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greatly reduce load time since you don't need to read the file from a disk. For a smaller node application |
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like my blog the benefits of using the server side cache nearly cut my load time in half. |
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Make sure that you don't accidentally cache a dynamic page like the CMS page in your admin section. |
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To demonstrate the performance increase of this method, I restarted my web server (clearing the cache) and ran |
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a speed test which ran three trials. The first two trials were slow since the server didn't cache anything. However, |
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the third trial ran extreamly fast since all the contents were in the server's cache. |
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## 5: Enable Compression |
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Compressing content before it is transferred over the internet can significantly decrease the loading time of your |
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website. The only trade off of this approach is that it takes more CPU resources, however, it is well worth it for the |
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performance gains. Using Gzip on CSS and html can reduce the size by 60-70%. |
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If you are running an NGINX server, you can enable Gzip there. There is also a simple node module which will |
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use Gzip compression on an Express app. |
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#### Gzip on Express App |
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``` |
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npm install compression |
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var compression = require('compression') |
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app.use(compression()); |
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``` |
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## 6: Remove Unused CSS Definitions |
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If you use a css library like Bootstrap or W3CSS, you will have a ton of css classes which go |
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unused. The standard BootStrap css file is around 210kb. After I removed unused CSS definitions |
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the size of the BootStrap file was only 16kb. |
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There are tons of tools online, however, for my blog I used PurgeCSS which is a |
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node library. |
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This command will install PurgeCSS for CLI (command line interface). |
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``` |
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npm i -g purgecss |
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``` |
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This is an example of how you would use PurgeCSS to remove unused css definitions. |
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``` |
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purgecss --css css/app.css --content src/index.html --out build/css/ |
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``` |
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PurgeCSS CLI options. |
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``` |
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purgecss --css <css> --content <content> [option] |
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Options: |
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--con, --content glob of content files [array] |
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-c, --config configuration file [string] |
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-o, --out Filepath directory to write purified css files to [string] |
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-w, --whitelist List of classes that should not be removed |
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[array] [default: []] |
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-h, --help Show help [boolean] |
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-v, --version Show version number [boolean] |
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``` |
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This is not the ideal solution since some CSS definitions may be used on some pages |
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yet unused on other pages. When running this command be sure to select a page which |
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uses all of your CSS to prevent loosing some CSS styling on certain pages. |
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You don't have to use this through the command line, you can run this directly in your |
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node app to make this automated. Check out their [documentation](https://www.purgecss.com/) to |
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learn more. |
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## 7: Minify CSS and Javascript |
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This is possibly the easiest thing you can do to reduce the size of your website. |
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Essentially you just run your CSS and JavaScript through a program which strips out |
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all unnecessary characters. |
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Ex Of Minified CSS: |
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``` |
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.bg-primary{background-color:#3B536B!important}#mainNav{font-family:Montserrat,'Helvetica Neue',Helvetica,Arial,sans-serif;font-weight:700;text-transform:uppercase;padding-top:15px;padding-bottom:15px}#mainNav .navbar-nav{letter-spacing:1px}#mainNav .navbar-nav li.nav-item a.nav-link{color:#fff}#mainNav .navbar-nav li.nav-item a.nav-link:hover{color:#D2C0FF;outline:0}#mainNav .navbar-toggler{font-size:14px;padding:11px;text-transform:uppercase;color:#fff;border-color:#fff}.navbar-toggler{padding:.25rem .75rem;font-size:1.09375rem;line-height:1;background-color:transparent;border:1px solid transparent;border-radius:.25rem}.table .thead-dark{color:#fff;background-color:#513E7D;border-color:#32383e}footer{color:#fff}footer h3{margin-bottom:30px}footer .footer-above{padding-top:50px;background-color:#3B536B}footer .footer-col{margin-bottom:50px}footer .footer-below{padding:25px 0;background-color:#3B536B} |
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``` |
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There are Node libraries which can minify CSS and Javascript, however, if you are really |
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lazy, just use a website like [this](https://cssminifier.com/). |
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## 8: Keep Minimal JavaScript |
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Ignoring the amount of Node dependencies you have, it is critical to minimize |
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the amount of dependencies the client needs. I was able to completely remove |
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BootStrap's javascript and Jquery by simply writing a javascript function for my nav bar. |
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This reduced the size of my website by 100kb. |
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``` |
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const e = document.querySelector(".navbar-toggler"); |
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const t = document.querySelector(".navbar-collapse"); |
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e.onclick = function() |
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{ |
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if (e.getAttribute("aria-expanded") == "false") |
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{ |
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t.classList.remove('collapse'); |
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e.setAttribute('aria-expanded', true); |
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} |
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else |
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{ |
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e.setAttribute("aria-expanded", false); |
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t.classList.add('collapse'); |
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} |
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} |
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``` |
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You should also debate how much you need 3rd party scripts like Google Analytics. |
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In most cases people don't full take advantage of Google Analytics, a simple backend analytics |
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service would work just as good while saving the client load time. |
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## Resources |
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- [Pingdom Speed Test](https://tools.pingdom.com/) |
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- [Google Website Speed Test](https://developers.google.com/speed/pagespeed/insights/) |
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- [Code to My "Optimized" Node Blog](https://github.com/jrtechs/NodeJSBlog) |
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- [Purge CSS](https://www.purgecss.com/) |
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- [CSS and JavaScript Minifier](https://www.minifier.org/) |
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jrtechs
6 years ago
