What’s interesting is that—when it comes to prototyping—our usual front-end priorities can and should go out the window. The priority now is speed. If that means sacrificing semantics or performance, then so be it. If I’m building a prototype and I find myself thinking “now, what’s the right class name for this component?”, then I know I’m in the wrong mindset. That question might be valid for production code, but it’s a waste of time for prototypes.
I love the way that Jeremy phrases all of this and how he describes that these two environments require entirely separate mindsets. When prototyping, for instance, we can probably overlook optimizing for accessibility or performance and even let our CSS standards slip in order to get something in the browser and test it as quickly as possible.
I reckon that the first time a designer and/or front-end developer writes code, it should never be in a production environment. Having the leeway and freedom to go crazy with the code in a safe environment focuses your attention on the design and making it compatible with a browser’s constraints. After this, you can think about grooming the code from a hot, steaming heap of garbage into lovely, squeaky-clean, production-ready poetry. Translating the static mockups into an interactive prototype is the first step, but it’s vital to have a next step to enforce your code standards.