Question

39

Javascript object creation on the fly

rated 0 times [ 43] [ 4] / answers: 1 / hits: 15862 / 15 Years ago, wed, january 6, 2010, 12:00:00

I'm sure I've seen some examples of this in jquery. But for me, the following code does not work. The firebug debugger tells me that: 'Location is undefined'. Could you tell me if this is possible?

function ResolveGeoCode() {

    var Location;

    Location.Ad1 = Hello ;

    Location.Ad2 = World;



    return Location;

}



var loc = ResolveGeoCode();

var String1 = loc.Ad1; //This contains Hello ?

var String2 = loc.Ad2; //This contains World?

Could a name be given to this type of feature I'm looking for?

Thanks.

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jarrodfletchers

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answered 15 Years ago arturo · Accepted Answer

This is what's happening:

function ResolveGeoCode() {

    // Location is declared, but its value is `undefined`, not `object`

    var Location;

    alert(typeof Location); // <- proof pudding



    // Failing here because you're trying to add a 

    // property to an `undefined` value



    Location.Ad1 = Hello ; 

    Location.Ad2 = World;



    return Location;

}

Fix it by declaring Location as an empty object literal before trying to add properties to it:

function ResolveGeoCode() {

    var Location = {};

    alert(typeof Location); // now it's an object



    // Programmatically add properties

    Location.Ad1 = Hello ; 

    Location.Ad2 = World;



    return Location;

}

If you know the properties and their corresponding values ahead of time, you can use a more inline approach:

function ResolveGeoCode() {

    var Location = {

        Ad1: Hello ,

        Ad2: World

    };



    // ...further manipulations of Location here... 



    return Location;

}

Read here for more on object literals.