MERN – JavaScript basic

Revisiting JS basics resently.

1. JavaScript 的灵活性与“陷阱”

(JavaScript’s Flexibility and Its “Traps”)

JavaScript 是一门非常灵活的语言——动态类型、函数是一等公民、原型链继承……这些特性让它能快速开发原型，但也导致了很多初学者的“踩坑现场”。
(JavaScript is an extremely flexible language—dynamic typing, functions as first-class citizens, prototype-based inheritance… These features make it great for rapid prototyping, but also lead to plenty of beginner “gotchas.”)

最让我印象深刻的是：

• Hoisting（提升）： 变量声明会被提前，但赋值不会，这一点如果不熟悉很容易出 bug。
  (Variables are hoisted but their assignments are not—this can easily cause subtle bugs if you’re not careful.)
• this 指向： 发现 this 的指向取决于调用方式，而不是定义位置。这点和 Java 很不一样。
  (I realized that this depends on how a function is called, not where it’s defined. This is very different from Java.)
• 闭包（Closure）： 在函数外访问函数内的变量，这种“记忆能力”很神奇，也很强大。
  (The ability to access inner function variables from outside—closures—felt both magical and powerful.)

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2. 思维上的转变

(Shifting My Programming Mindset)

学 JavaScript 让我不得不转变一些原本写 Java 的思维习惯：
(Learning JavaScript forced me to shift some of my habits from writing Java code:)

• 面向对象 vs. 原型链继承
  JavaScript 没有传统的类继承，而是基于原型的继承模型。最初觉得有点混乱，但理解 Object.create() 和 __proto__ 后，慢慢顺了。
  (JavaScript doesn’t have classical inheritance; it’s prototype-based. It felt confusing at first, but understanding Object.create() and __proto__ helped a lot.)
• 异步处理的思路
  在 JavaScript 里，异步是“原生”的。回调、Promise、async/await 是三种不同层级的异步编程体验。
  (Asynchronous programming feels “native” in JavaScript. Callbacks, Promises, and async/await offer three very different levels of handling async operations.)
• 函数式思维的渗透
  之前很少用高阶函数。现在 map、filter、reduce 成了处理数组的常用工具。
  (Previously I rarely used higher-order functions. Now map, filter, and reduce are my go-to tools for working with arrays.)

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3. JS 给我的启发

(What JavaScript Taught Me)

• JavaScript 不是完美的语言，但它非常“贴近开发者思路”。
  (JavaScript isn’t a perfect language, but it’s very close to how developers think.)
• 它的灵活性既是优势，也是坑点。学会规范化使用它非常重要（比如避免滥用 var，善用 let/const）。
  (Its flexibility is both a strength and a weakness. Learning how to use it in a disciplined way is critical—like avoiding var in favor of let/const.)
• 如果把 JS 学通了，对理解其他语言的内存、作用域、异步也有很大帮助。
  (If you truly master JS, it will deepen your understanding of memory, scope, and async behavior in other languages too.)

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我的下一步计划

(My Next Steps)

我打算学习一些ES6。他有一些新特性能帮助我写出更简洁、更易维护的代码。
(Next, I plan learn some ES6. It has some modern features which will help me to write cleaner and mode maintainable code.)

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结尾感想

(Final Thoughts)

回头看这几天的学习，JS 基础确实不像最初以为的那么“简单”。它有很多历史遗留的问题，也有不少设计得非常巧妙的地方。总之，开始有点理解为什么大家说“你永远学不完 JS”了。😂
(Looking back, JS basics aren’t as “simple” as I initially thought. It has its share of historical quirks, but also some very elegant designs. I’m starting to understand why people say: “You never really finish learning JS.” 😂)