外部变量作用域在javascript函数内部不可用

Question

How to access the outer variable inside the inner javascript function , please check my code below i need to access "index" variable inside app() function .

 function validate()
    {

    for (index = 0; index < results.length; index++) {
        var parsedData_1;
        var provider = results[index].get("provider");                          
        var user = results[index].get("user");          
        var addresses = user.get("addresses");

        var address = addresses[1];

        var GameScore = Parse.Object.extend("Address");
        var query = new Parse.Query(GameScore);         
        var data = JSON.stringify(address);     


        var parsedData = jQuery.parseJSON(data);            
        query.get(parsedData.objectId, {
        success: function(resultadr) {          

        var res = JSON.stringify(resultadr);
        var parsedData_1 = jQuery.parseJSON(res);   
        var apartment = parsedData_1.apartment;

        apa(apartment);

        },
        error: function(object, error) {            
        alert('error');             

        }
        });         

        function apa(apartment)
        {
        alert(index); [I'm not getting the index value inside this function]
        alert(apartment);

        }

    }

    }

Inside the function apa() i need the index count , but im unable to get it , please help how to access the outer value inside the function.

Answer 1

据我所知apa（）无法访问index变量，所以我将其放在函数调用的参数中，然后像这样调用apa（）

apa(apartment, index);

Answer 2

The problem is that you are using closures to access the index, thus the lastest value assinged to that variable is accessible in the app function. For example, if results.length equlas 11, index in app function will always be 11.

The soltion is to declare a variable inside the for loop, assign the index value to that variable, and pass the variable to app function.

//Create a factory function for the app function
//Outside the for loop.

var createAppFunc = function (i) { 
    return function () { 
        console.log(i); 
    };
};
for (var index = 0, l = results.length; index < l; index++)
{
    var newVar = index;
    var app = createAppFunc(index); //Now, app is a function.
}

Good Luck :).

Answer 3

You can use Function.bind() to pass the actual index as first argument to the sucess-callback. There you can get it and pass it along as parameter to function apa() . And: use keyword var for the index in for() .

function validate() {

    for (var index = 0; index < results.length; index++) {

        /* all the vars here */

        query.get(parsedData.objectId, {
            success: function(idx, resultadr) {
                var res = JSON.stringify(resultadr);
                var parsedData_1 = jQuery.parseJSON(res);   
                var apartment = parsedData_1.apartment;
                apa(idx, apartment);
            }.bind(null, index),
            error: function(object, error) {            
               alert('error');             
            }
        });

        function apa(index, apartment) {
            console.log(index); console.log(apartment);
        }

    }
}

The first parameter (here: null) of bind() sets the context of the bound function. Whatever you pass in will be accessible in the success-callback by the keyword this .

Answer 4

我认为每次调用该函数时，下一个循环调用都会损害该调用。因此，最后该方法将仅被调用一次。

Answer 5

您可以全局声明索引变量，然后所有函数都可以访问它