JSFiddle - React, Tailwind, and code Playground

by ysuper

HTML

<p>
閉包
</p>
<a href="https://developer.mozilla.org/zh-TW/docs/Web/JavaScript/Closures" target="_blank">MDN Web Docs（舊稱Mozilla Developer Network、Mozilla Developer Center，簡稱MDN）</a>

JavaScript

/* function counter(){
  var count = 0;

  return function(){
    return ++count;
  }
} */

var counter = () => {
  var count = 0;
  return () => ++count;
}

var countFunc = counter();
var countFunc2 = counter();

console.log( countFunc() );   // 1
console.log( countFunc() );   // 2
console.log( countFunc() );   // 3

console.log( countFunc2() );   // 1
console.log( countFunc2() );   // 2