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Closures in JavaScript

JavaScript

in-loop.js Raw #

// https://diskuse.jakpsatweb.cz/?action=vthread&forum=8&topic=103393

for(var i=0; stylNameArray.length>i; i++) {
   (function(){
     var n = i;
     neco[i].onclick = function() {
      zmenaStylu("styl_pozadi_oken_0" + n);
    }
   })();
} 


for(var i=0; stylNameArray.length>i; i++) {
   (function(i){
     neco[i].onclick = function() {
      zmenaStylu("styl_pozadi_oken_0" + i);
    }
   })(i);
}

counter-instances.js Raw #

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

var counter1 = makeCounter();
var counter2 = makeCounter();
alert(counter1.value()); /* Alerts 0 */
counter1.increment();
counter1.increment();
alert(counter1.value()); /* Alerts 2 */
counter1.decrement();
alert(counter1.value()); /* Alerts 1 */
alert(counter2.value()); /* Alerts 0 */

counter.js Raw #

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

closure.html Raw #

<p id="demo">0</p>

<script>
var add = (function () {
    var counter = 0;
    return function () {return counter += 1;}
})();

function myFunction(){
    document.getElementById("demo").innerHTML = add();
}
</script>