At PayPal we write a lot of javascript that ends up running on other websites and other domains. The prime example of this is checkout.js, the integration script for our entire checkout experience, which allows merchants to embed our button and checkout flow seamlessly into their sites. There are a huge number of perils and pitfalls around running our code on third-party sites, though: We absolute
![Introducing PayPal’s open-source cross-domain javascript suite](https://cdn-ak-scissors.b.st-hatena.com/image/square/9eab960ad12eb4967ce810d1bc6eeaf993db0cd2/height=288;version=1;width=512/https%3A%2F%2Fmiro.medium.com%2Fv2%2Fresize%3Afit%3A1088%2F1%2AK3KFLwLUrc17P5Ol5aa_aA.png)