javascript - updating global object variables via a function

Weird problem here, I'm trying to use a global function to update my settings object, example:

    var Settings = new Object;
    Settings.savepos = 'true';

    function UpdateSetting(obj,value){
        eval("Settings.obj = value");
        alert(Settings.savepos);
    }

The obj is the key of the object, meaning if I call the function with

UpdateSetting('savepos','false')

the alert will always just give me true, how do I convert that eval or any alternative so it will update sett开发者_运维百科ings object's key with the value?

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You are setting Settings.obj, not setting.savepos.

Try this instead:

function UpdateSetting(obj,value){
    Settings[obj] = value;
    alert(Settings.savepos);
};

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You are always changing the "obj" key of the object to equal value, which is likely to be undefined (or, at least, not defined to what you want) in the context eval() executes it in. So, you have two options. First, you can keep using eval() (although i don't recommend it because it's more pain than necessary):

var Settings = new Object;
Settings.savepos = 'true';

function UpdateSetting(obj,value){
    eval("Settings."+obj+" = '"+value+"'");
    alert(Settings.savepos);
}

Or, as numerous other have suggested, you can use the array operator[] to access the property by key:

var Settings = new Object;
Settings.savepos = 'true';

function UpdateSetting(obj,value){
    Settings[obj] = value;
    alert(Settings.savepos);
}

---

1. you dont need an eval
2. you're setting .obj, not .savepos (there is no interpolation for the string)
3. you may be calling it wrong.

I'm not exactly sure why you don't just set the value directly (eg. Settings.savepos=false;).
You can attach the function to that object to do something similar:

var Settings            =  new Object;
Settings.savepos        =  true;
Settings.UpdateSetting  =  function (prop,value){this[prop] = value;}

Settings.UpdateSetting('savepos',false);

---

You should be able to use array notation on the object. Underneath it's just a keyed hash.

Try:

Settings[obj] = value;

I'd also suggest passing values as they are, i.e. string, int, etc:

UpdateSetting('key_name', false);