Closures store references to the outer function’s variables

They do not store the actual value. 
Closures get more interesting when the value of the outer function’s variable changes before the closure is called. And this powerful feature can be harnessed in creative ways, such as this private variables example first demonstrated by Douglas Crockford:


by KevinIsNowOnline

JavaScript

function numberHolder() {
    var currentValue = 9999;
    return{
        getValue: function(){
            return currentValue;
         },
        
        setValue: function(newNum) {
             currentValue = newNum;    
        }
}
};

var newHolder = numberHolder();
console.log(newHolder.getValue());
newHolder.setValue(1000);
console.log(newHolder.getValue());