Javascript – העברת פרמטר ל- Callback מתוך לולאה

קטגוריות: Javascript, תכנות

נעבור לאנגלית:

// this is bad: 
// same item is passed to the callback because it's by reference
// outcome: only "George" will be dealt with 3 times
var arr = ["AVI", "Benz", "George"];
for (var i=0; i < arr.length; i++) {
	var item = arr[i];
	api.do_something(function(result) {
		callback(result,item);
	});
}

// this is the correct way: 
// using a self invoked function
// item is copied every iteration into the callback as param
var arr = ["AVI", "Benz", "George"];
for (var i=0; i < arr.length; i++) {
	var item = arr[i];
	(function(item) {
		api.do_something(function(result) {
			callback(result,item);
		});
	})(item);
}