Feng Hua Frontend Engineering Documentation

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. Key characteristics include:

• Compilation: TS cannot run directly in browsers or Node.js (except Deno); it must be compiled to JS.
• Static Typing: Unlike JS's dynamic typing, TS requires variables to have determined types at development time, catching type errors before execution.
• Superset: TS supports all JavaScript syntax and adds additional features, meaning all valid JS code is valid TS code.

Web Components is a native browser technology for creating encapsulated, reusable custom HTML elements. It consists of three primary pillars:

1. Custom Elements: JavaScript classes that extend HTMLElement (or other specific DOM objects) to define new HTML tags. They include four lifecycle hooks: connectedCallback() (mount), disconnectedCallback() (unmount), adoptedCallback() (moved to a new parent), and attributeChangedCallback() (attribute change).
2. Shadow DOM: A private, isolated DOM tree attached to a custom element. It prevents styles and scripts inside the component from leaking out and vice versa.
3. HTML Templates: Uses <template> and <slot> tags. <template> holds markup that isn't rendered until instantiated, and <slot> acts as a placeholder for external content passed into the component.

CSS (Cascading Style Sheets) is a descriptive, declarative stylesheet language used to style content rendered by browsers, such as HTML and SVG. It allows developers to control fonts, colors, layout, typography, and add animations to enhance user experience and interactivity.

Learning CSS involves mastering several key components, categorized into basic and advanced levels:

Basic Components:

• Selectors
• Styles
• Positioning
• Layout
• Media Queries
• Animations

Advanced Components:

• Box Model
• BFC (Block Formatting Context)
• Selector Priority/Specificity
• 2D/3D Space
• Variables
• Functions
• Color Representations
• Build Tools
• UI Libraries

Web Components is a native browser technology for creating reusable, encapsulated custom HTML elements. It consists of three primary pillars:

1. Custom Elements: Created by extending HTMLElement (or other DOM objects). They provide lifecycle hooks: connectedCallback() (mount), disconnectedCallback() (unmount), adoptedCallback() (moved), and attributeChangedCallback() (attribute change).
2. Shadow DOM: A separate, isolated DOM tree attached to a custom element. It prevents styles and scripts from leaking in or out of the component.
3. HTML Templates: Uses <template> and <slot> tags. The <template> defines the structure and style, while <slot> acts as a placeholder that can be replaced by real elements from the parent DOM.

Vue 3 introduces several architectural and performance improvements over Vue 2:

• Performance: Execution speed is approximately 1.5x faster than Vue 2.x.
• Bundle Size: Smaller bundle sizes due to better Tree-shaking support and the removal of unused APIs (e.g., inline-template, filter).
• TypeScript Support: The entire source code was rewritten in TypeScript, providing better type inference and maintainability.
• Project Structure: Uses a monorepo to manage multiple packages, making functional modules clearer and easier to test/release independently.
• Composition API: A new set of function-based APIs that allow for better logic organization, encapsulation, and reuse compared to the Options API.

CSS (Cascading Style Sheets) is a descriptive, declarative stylesheet language used to style content rendered by browsers, such as HTML and SVG. Unlike programming languages, CSS focuses on the visual presentation of elements, including colors, layout, typography, and animations to enhance user interaction.

CSS is categorized into basic and advanced components:

Basic Components:

• Selectors
• Styles
• Positioning
• Layout
• Media Queries
• Animations

Advanced Components:

• Box Model
• BFC (Block Formatting Context)
• Selector Specificity/Priority
• 2D/3D Space
• Variables
• Functions
• Color Representations
• Build Tools
• UI Libraries

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. Key characteristics include:

• Compilation: TS cannot run directly in browsers or Node.js (except Deno); it must be compiled to JS.
• Static Typing: Unlike JS's dynamic typing, TS requires variables to have determined types at development time to prevent type-related errors.
• Superset: TS supports all JavaScript syntax, meaning any valid JS code is valid TS code.

TypeScript is a typed superset of JavaScript that compiles to plain JavaScript. Key characteristics include:

• Compilation: TS cannot run directly in browsers or Node.js (except in Deno) and must be compiled to JS.
• Static Typing: Unlike JavaScript's dynamic typing, TS requires variables to have determined types at development time, allowing errors to be caught before execution.
• Superset: TS supports all JavaScript syntax and adds additional features, meaning all valid JS code is valid TS code.

Vue 3 introduces several significant upgrades over Vue 2.x:

• Performance: Execution speed is approximately 1.5x faster than Vue 2.x.
• Bundle Size: Smaller bundle sizes due to better tree-shaking and on-demand compilation.
• TypeScript Support: The entire framework is rewritten in TypeScript, providing better type inference and developer tooling.
• Composition API: A new set of functional APIs that allow for better logic organization, encapsulation, and reuse compared to the Options API.
• Advanced APIs: Exposure of lower-level APIs and more advanced built-in components.

In CSS, every HTML element is treated as a rectangular box consisting of four areas from the inside out:

1. Content Area: The actual content, determined by width and height.
2. Padding Area: The space between the content and the border, set via padding.
3. Border Area: The boundary between padding and margin, set via border.
4. Margin Area: The space between the border and adjacent boxes, set via margin.