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MDNの定義

LexicalScoFran？

function init() {
  var name = "Mozilla"; 
  function displayName() { // displayName() 은 내부 함수이며, 클로저다.
	console.log(name) //Mozilla
  }
  displayName();
}
init();

味わう

function makeAdder(x) {
  var y = 1;
  return function(z) {
    y = 100;
    return x + y + z;
  };
}

var add5 = makeAdder(5);
var add10 = makeAdder(10);
console.log(add5(2));  // 107 (x:5 + y:100 + z:2)
console.log(add10(2)); // 112 (x:10 + y:100 + z:2)

利用する

var counter = (function() {
  var privateCounter = 0;
  function changeBy(val) {
    privateCounter += val;
  }
  return {
    increment: function() {
      changeBy(1);
    },
    decrement: function() {
      changeBy(-1);
    },
    value: function() {
      return privateCounter;
    }
  };
})();

console.log(counter.value()); // logs 0
counter.increment();
counter.increment();
console.log(counter.value()); // logs 2
counter.decrement();
console.log(counter.value()); // logs 1