As a part of Udacity's Front-end Web Developer Nanodegree I was challenged to optimize a website created by course developer Cameron Pittman that contained many performance-related issues.

Cam's original live version can be found here This is a link to the GitHub repo

My optimized version is linked here This is a link to my GitHub repo

The index page orginially had a Google Page Speed Insights score of 28/100 mobile and 30/100 desktop. After implementing the following optimizations I was able to achieve a score of 93/100 on mobile and 94/100 on desktop.

Minified the Javascript using this tool and added the async attribute to all script tags.

Minified the CSS using this tool and inlined it as well. Added the media = "print" attribute to the external print style sheet linked.

Large images were compressed and re-sized using this site.

Removed the link to Google Fonts and instead applied the font style directly in the CSS body, button, input, select, textarea { font-family: 'Open Sans', sans-serif; color: #333; }

There were two major assignments for this page:

1. Resize the pizzas in < 5ms
2. Achieve a consistent frame rate at 60fps when scrolling

Initially the pizzas were resizing at 211.8ms (yikes!). After implementing the following code the pizzas are now resizing at 0.8ms. See lines 401-452

Initialls the average time to generate the last 10 frames was around 60ms, after optimizations this number decreased to about 0.6ms for 10 frames. By utilizing Chrome Dev Tools Timeline I was able to track the fps and reduce jank. Specifically changes in the updatePositions() function as well as adding a scroll event listener to call the rAF so the animations are requested when scrolling. This link was a great source. See lines 494-580 for detailed comments of changes.

• querySelector and querySelectorAll were replaced with getElementById and getElementsByClassName which are much faster.
• Several variables were decared and calculated outside of loops where possible to enhance performance.
• Generate 50 pizzas on page load instead of 200 to increase speed

After reading these tips the following style attributes were added to the .movers element:

-webkit-transform: translateZ(0);
will-change: transform, opacity;```