クロージャ

closure.js

function newCounter() {
 var i = 0;
 return function() {
 i = i + 1;
 return i;
 }
}
var c1 = newCounter();
var c2 = newCounter();
console.log(c1()); // 1
console.log(c1()); // 2
console.log(c2()); // 1