在javascript中更新事件函数中的全局变量

Question

I think this question has been asked before but i was unable to find an answer, maybe I'm lacking the good words to describe my problem.

I have a loop in which, each iteration i create an object and I add an event listener which callback function uses the created object.

for(var i in items)
{
    x = new SomeClass(i)

    someAPI.event.addListener(i, 'click', function(ev){
        x.someMethod()
    }); 
}

What happens, and I understand why, is the variable x within the event function definition is evaluated only when the event is triggered, and x is equals to the last value that has been affected to this name, which is the value given at the last iteration.

I would like to know how is it possible to get the wanted behavior, which is getting the current value of x in the loop, within the event function definition. Thanks.

Answer 1

for(var i in items) {
    (function(j) {
        var x = new SomeClass(j);

        someAPI.event.addListener(j, 'click', function(ev){
            x.someMethod()
        });
    })(i);
}

The key is the var keyword, creating a new instance of the class on each iteration.
I added the IIFE to keep the value of i constant and to create a new scope on each iteration.