Question

I’m trying to use a string as a reference to a variable to pass into a function. For example:

var names = ['Peter', 'John'],

var hasName = function(name){
    var params = ['names'];
    return $.inArray(name, eval( params[0] )) === -1;
};

How to avoid eval()?

EDIT:

The string from params[0] is comming from a data-qval of an input in my html. The array that contains the actual data can be declared anywhere, params[0] is just a reference to that array passed in as string in data-qval, it’s a parameter. I pasted my plugin’s code here .

http://pastebin.mozilla.org/1598528 Line 101.

Full example: http://jsfiddle.net/elclanrs/ZsS2D/29/

It currently works, I’m just looking for a way get rid of eval()…

Answer 1

In that particular case, just use names:

var names = ['Peter', 'John'],
var hasName = function(name){
    var params = ['names'];
    return $.inArray(name, names ) === -1;
};

(See also the note below.) (Your edit makes the above not applicable.)

If you’re trying to look up the names array in some container using the string "names", you’d have to have a reference to the container, e.g.:

var obj = {
    names: ['Peter', 'John'
};
var hasName = function(name){
    var params = ['names'];
    return $.inArray(name, obj[params[0]] ) === -1;
};

If there is no container other than the variable scope in which you’re doing this, you’ll have to use eval. But you can (and usually should) adjust things so you have a container (as above) so you can avoid it. Note that if names is declared at global scope, you do have a container (window).

So to summarize:

1. If names is a var at global scope (or an implicit global), window[params[0]] will give you a reference to it.

2. If names is already in some container object, you can use container[params[0]] to get a reference to it.

3. If names is a var within a function, you cannot get at it using a runtime string without eval; ideally, rather than var names = [...];, use var container = {names: [...]}; and then you can use container[params[0]].

---

Note that your function is called hasName, but it returns true when the array doesn’t have the name and false when it does. You probably want !== -1, not === -1.