JavaScript Scope All In One

JavaScript Scope All In One

1. Global Scope / 全局作用域
2. Script Scope / 脚本作用域
3. Local Scope / 局部作用域 (函数作用域)
4. Block Scope / 块级作用域 ( { } 作用域)
5. Catch Block Scope / 捕获块级作用域 ( try...catch 作用域)
6. Closure Scope / 闭包作用域
   7. Promise Scope ???

demos

debugger

// 1. Global Scope / 全局作用域
var a = 1;
// 2. Script Scope / 脚本作用域
let b = 2;
// 3. Local Scope / 局部作用域
(function(){
  var bb = 2;
  // 函数作用域 ???
  let c = 3;
})();


// ES6 let 等价于 ES5 IIFE ???

// 1. Global Scope / 全局作用域
var a = 1;
// 2. Script Scope / 脚本作用域
let b = 2;
// 3. Local Scope / 局部作用域 (函数作用域)
(function(){
  var bb = 2;
  // ???
  let c = 3;
})();
// ES6 let 等价于 ES5 IIFE ???

// 4. Block Scope / 块级作用域 ( `{ }` 作用域)
for (const item of ['block']) {
  var a1 = item;
  let b1 = item;
  const c1 = item;
  console.log(`a1,b1,c1 =`, a1,b1,c1);
}

// 5. Catch Scope / 捕获作用域 ( `try...catch` 作用域)
try {
  throw new Error(`catch scope ❌`);
} catch (error) {
  let err = error;
  console.error(`err =`, err);
}

// 6. Promise Scope ???
Promise.resolve(() => {
  var p1 = 1;
  let p2 = 2;
  const p3 = 3;
  console.log(`p1,p2,p3 =`, p1,p2,p3);
});

new Promise((resolve, reject) => {
  resolve(`200 ✅`);
}).then(res => {
  var pRes = res;
  console.log(`pRes`, pRes);
}, err => {
  var pErr = err;
  console.log(`pErr`, pErr);
}).catch(err => {
  var cRrr = err;
  console.log(`cRrr`, cRrr);
}).finally(() => {
  var loading = false;
  console.log(`loading`, loading);
});

new Promise((resolve, reject) => {
  reject(`404 ❌`);
}).then(res => {
  var pRes = res;
  console.log(`pRes`, pRes);
}, err => {
  var pErr = err;
  console.log(`pErr`, pErr);
}).catch(err => {
  var cRrr = err;
  console.log(`cRrr`, cRrr);
}).finally(() => {
  var loading = false;
  console.log(`loading`, loading);
});

react-devtools

function injectScriptAsync(src) {
  const script = document.createElement('script');
  script.src = src;

  script.onload = function () {
    script.remove();
  };

  nullthrows__WEBPACK_IMPORTED_MODULE_0___default()(document.documentElement).appendChild(script);
}

chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/prepareInjection.js

chrome-extension://fmkadmapgofadopljbjfkapdkoienihi/build/installHook.js

https://github.com/facebook/react/tree/main/packages/react-devtools#the-react-tab-doesnt-show-up

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refs

https://github.com/xgqfrms/learning/issues/145

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