Article · 20 min read

The Cost Of JavaScript

Addy Osmani · Addy Osmani (Dev Channel, Medium) Free Intermediate

Every kilobyte of JavaScript costs far more on a cheap phone than on your machine, because the phone has to download it and then grind through parsing it on a weak CPU. Osmani shows the 2 to 5x difference in parse time between a flagship and an average phone, and gives concrete ways to ship less. This is the case for keeping your app light, backed by measurements rather than opinion.

• Download size and CPU parse time both punish low end devices twice over
• Ship less code first, then defer and split what remains
• Measure on a real budget phone, not on your dev machine