❗global var / function is global object property❗️

🚧 under construction

• JS ⟩ scope ⟩ global ⟩ variable ⟩ var ⟩ is global object property

• JS ⟩ variable ⟩ var ⟩ global var is global object property

(side effect)

global var/ global function are implemented as global object property❗

📗 參考

• YDKJS: Scope & Closures (v.2) ⟩

👥 相關

• ✅stop using var❗️

• 🔰global scope

• ❗global var is a global object property, and vice versa.

• ⚖️ compare： module scope - no module-wide scope object.

💈範例

• replit：global var is global object property

const { log } = console;
const isCurrentlyInGlobalScope = () => this === globalThis;

// log( prop );                // ReferenceError: (property is not hoisted) ⛔ 
log( topLevelVar );              // undefined     : (var is hoisted but uninitialized)

// ⭐️ a global object property is like a global var (but not hoisted)
globalThis.prop = 42;            //                // define new property
log(prop, typeof prop);          // 42, number     // it acts like a global var
prop = 36;                       //                // we can change it
console.log(globalThis.prop);    // 36             // change will reflect on global object

// ⭐️ a global var is a global object property

// ❗ but in Node.js:
//    • top-level scope is NOT global scope
//    • top-level var will NOT be reflected in global/module context.
var topLevelVar = 'hello';
log(globalThis.topLevelVar);     // undefined❗
log(module.exports.topLevelVar); // undefined❗

// log
;[
    globalThis === global,        // true

    // current context
    isCurrentlyInGlobalScope(),   // false
    this === module.exports,      // true

].forEach(x => console.log(x));

🗣 討論

• Is there any difference between a global variable and a property of the Global Object

🚧

• global function