CODEWITHSUNDEEP
javascriptgoogle-maps
scooby
scooby

Reputation: 603

problem while passing function as parameter in Javascript

function initialize(final) {
        /* ........ */
        var address_array = final.split('~');


        for (var count = 0; count < address_array.length; count++) 
        {
            if (geocoder) {
                geocoder.getLatLng(
                    address_array[count],
                    function (point) {
                        if (!point) {
                            alert(address_array[count] + " not found");
                        }

All I want is the alert to work over here, in the last line.

Suppose address_array has 3 values, i.e address_array.length is 3. But the alert is always showing undefined not found. I am assuming address_array[count] cannot be accessed from this function. However when I try 

alert(address_array.length + " not found");

it says 3 not found. please help.

can anyone please help me regarding this issue?

function makeTheFunction(array, thisCount) { return function (point) { if (!point) { alert(array[thisCount] + " not found"); }

          else {
              var marker = new GMarker(point);
              map.addOverlay(marker);
              GEvent.addListener(marker, "click", function () {
                  marker.openInfoWindowHtml(array[thisCount] + "</b>");
              });
          }
      };
  }

the alert(array[thisCount] + " not found"); is working fine but it doenst seem to work when it goes into the else section ..marker.openInfoWindowHtml(array[thisCount] + "");

Upvotes: 2

Views: 276

Answers (2)

tofarr
tofarr

Reputation: 7841

Try:

function initialize(final) {
        /* ........ */
        var address_array = final.split('~');

        for (var count = 0; count < address_array.length; count++) 
        {
            doGeocode(address_array[count]);
        }
}

function doGeocode(value){
    if (geocoder) {
        geocoder.getLatLng(
        value,
        function (point) {
            if (!point) {
                alert(value + " not found");
            }
        }
     }
}

Upvotes: 1

T.J. Crowder
T.J. Crowder

Reputation: 1073968

This happens because your function is a closure over the count variable, and closures get an enduring reference to the variable, not a copy of its value as of when the function is defined. So all copies of the function see count as of the end of the loop, which is outside the range of the array -- hence the undefined.

What you want to do is create the function such that it closes over something that doesn't change.

var address_array = final.split('~');

for (var count = 0; count < address_array.length; count++) 
{
    if (geocoder) {
        geocoder.getLatLng(
            address_array[count],
            makeTheFunction(address_array, count)
        );
    }
}

function makeTheFunction(array, thisCount)
{
    return function(point) {
        if (!point) {
            alert(array[thisCount] + " not found");
        }
    };
}

We pass both the array reference and the count value as of each iteration of the loop into makeTheFunction, which creates the function as a closure over its arguments and returns that function. Now the function will show the right information, because the information it's closing over doesn't change. Note that as written, makeTheFunction can be outside of any other function so as to avoid having the closure close over anything else.

More about closures: Closures are not complicated

Upvotes: 5

Related Questions