What Is The Correct Way To "serialize" Functions In Javascript For Later Use

I have a 'library' of objects that I want to load on the fly from a database. Each object comes with its own special functions that are called at specific times depending on the ob

Solution 1:

Just use eval to recreate the function after loading it as a string. So if you deserialize an object myObj from JSON, and you have a property:

myObj = {
    ....
    function: "function() { ... }"
}

you can very easily turn it to a real function:

eval("myObj.func = " + myObj.func);

http://jsfiddle.net/kceTr/

Oh - I am not sure if that was an edit or I missed it before - but re: eval.

Eval is a tool. You want to store a function in a database. It really doesn't make much difference if you have to "eval" to turn it into code, or there was some other magic way to do it: if someone can change the data in your DB, then they can change a function.

If you need to store a function, then eval is your tool. It's not "bad" by nature, it's bad because it's easy to misuse. Whether you use it well or not is up to you.

Remember anything running on the client is still just running on the client. There's nothing a malicious person could do with eval, that they couldn't do with the Chrome debugger a lot more easily. Anyone can always run any code they want on the client, it's up to your server to decide how to handle what it receives. There's nothing safe on the client in the first place...

Solution 2:

Changing the prototype of the object is a half thought I have.

You've got your library like

library = {
  "myObj" : {"name" : "myObj", "type" : "myType", "function" : function () { } } //, etc
}

You've got an object (let's call it theObj) that you know is a myObj (due to a string maybe? property?)

theObj.__proto__ = library["myObj"];

That way you can execute

theObj.function(...);

jsfiddle example (it's rough!). Also, be careful with proto, it's deprecated (1) (2)

As to serializing the functions, can you get them in using a script tag that points to something serverside that slurps them from the db and returns the js? Just include them inline as you render the page (in a script block)? Or, if all else fails, eval should work, as long as you know that the functions you've got stored in the database are clean and safe.

Solution 3:

A better approach might be to serialize the object's properties when you "sleep" it, and "waking" the object by reattaching its properties to a new instance of the object with the appropriate methods defined.

Solution 4:

what you are doing with it is just fine. However, if i were you, for readability and tidyness, i would rather have the function created outside and simply have it assigned to your object key.

You don't need eval here. Instead do it this way whenever you want access to the stored function -

library.myObj.function()

Solution 5:

• You do your best in parameterising your functions, so that you end up with as little typologies as possible.
• Store them on the server in individual JS files, then load the needed file dynamically, by name.
• In the JSON, only store the name of the file that contains the function that you need. And, of course, you will be caching already loaded files, to go easy on the server.

Just my two cents.