cache eval() result

Question

In Javascript, is it possible to cache the results of eval.

For example it would be great if I could:

var str="some code...";
var code = eval(str);
//later on...
code.reExecute();

Answer 1

The result of the 'eval' call is to evaluate the javascript. Javascript (in browsers) does not offer any kind of 'compile' function.

The closest you could get (using eval) is:

var cached_func = eval('function() {' + str + '}');

Then you can call the cached_func later.

Answer 2

You can make str the body of a function and use New Function instead of eval.

var fn = new Function([param1, param2,...], str);

And reuse it by calling fn(p1, p2,...)

Or use eval, and make str be something like

var fn = eval("(function(a){alert(a);})")

Answer 3

Make a function that evaluates and stores the result in a cache object for asynchronous retrieval:

 var Cache = { } ;

 function evalString(string) {

     var evaluated = eval(string) ;
         Cache.evalResult = evaluated ;

 }

You may then call that code like this:

 Cache.evalResult(/* arguments */) ;

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On a side note, "eval is evil" as http://www.jslint.com will tell you, since it may open the door for external manipulation of your content. Why do you need to eval that function it in the first place?