• Frontend developer just implements the GUI, using the provided design, specification and consultations with colleagues/client for additional information.

• Frontend engineer first measures the client and all the monitors by using a Vernier caliper, calculates their mass, acceleration and other parameters.

Engineers reason

In a blog post Dominic differentiates engineer from programmer by explaining that an engineer, “…can reason about his subject.”

The engineer knows the subject very well — this is a given. A front-end developer should know his subject very well, too, but he doesn’t necessarily “reason about” his subject and try to gain a deep, intuitive understanding of how his subject works.

Developers do

The front-end developer doesn’t “reason about” HTML, CSS, and JavaScript. The developer writes the code, and it works well (hopefully). It should be DRY, scalable, performant, etc.

The developer is a brick-layer, a drywaller, or an roofer. The developer does things, but not necessarily with the understanding and reasoning behind it. Does the brick layer necessarily know why the walls are 8 feet tall; does the drywaller know why the walls in the main corridor are 12 feet long?

A front-end engineer understands the mechanics behind the code

The front-end engineer, through reasoning, isn’t just doing tasks. The front-end engineer knows why she wrote her code the way that she did. She takes stacking context into consideration when she uses transforms. She considers specificity when she picks a CSS methodology. She thinks about prototypal inheritance when she picks a JavaScript pattern. She considers the performance gains and losses between for-in and forEach.

Front-end developers can write good code. Front-end engineers can explain how good code works. They understand browser mechanics; how the browser parses CSS, forms the DOM, and compiles JavaScript. Front-end developers are more likely to fix things. Front-end engineers are more likely to solve things.

A front-end engineer creates

Engineers design materials, structures, and systems while considering the limitations imposed by practicality, regulation, safety, and cost[1]. In the world of front-end, the starkest contrast I can provide is that a front-end engineer can create plugins, tools, frameworks, utilities, patterns, and methodologies.

A developer can use plugins, tools, frameworks, utilities, patterns, and methodologies.

The reason that front-end engineers can create these things is because the engineer “reasons about the code”. The engineer can evaluate a problem and design a solution or system that conforms to the limitations around it.