CODEWITHSUNDEEP
javascripteval
Will Morgan
Will Morgan

Reputation: 4490

What's a more secure alternative for eval() when I just want to call a function?

I know PHP has call_user_func, I was just wondering if JavaScript had something similar, where the method I want to call is, for example: object.set$fieldID($fieldValue)

I would rather not go through if/else/switch blocks just to execute one line of code properly.

If it helps, I am using jQuery.

Upvotes: 3

Views: 3288

Answers (2)

Ionuț G. Stan
Ionuț G. Stan

Reputation: 179119

object["set" + $fieldID]($fieldValue);

Some reading material for the above: Member Operators on MDC.

Some advanced methods include Function.prototype.call and Function.prototype.apply. The first is somehow equivalent to PHP's call_user_func() while the latter is somehow equivalent to PHP's call_user_func_array().

The difference between PHP's functions and JavaScript's is that JavaScript allows you to call methods of some object in the context of another object. This is done through the use of the first argument of call() and apply().

An equivalent for the above example, but using call() and apply() looks like this:

object["set" + $fieldID].call(object, $fieldValue);
object["set" + $fieldID].apply(object, [$fieldValue]);

The first argument must be object otherwise the method will be executed with the this pointer bound to the global object, window in the case of browsers.

Upvotes: 9

Justin Johnson
Justin Johnson

Reputation: 31300

@lonut is correct. More generally though, if you want to call functions that aren't a part of an explicit object (e.g.: global), you can call them on the window object:

var foo = function() { alert(1); };
window['foo']();

since all objects are contained in window.

Another example:

var object = function() { this.method = function() { alert(2); }; }
var instance = new object();
window['instance']['method']();

Upvotes: 4

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