changing string to a function in javascript (not eval)

you want to use the Function constructor directly, as Anders said. All arguments are strings. The last argument is the body of the function, any leading arguments are the names of the arguments the function takes.

To borrow from Anders' example,

var multiply = new Function("x", "y", "return x * y");

would be like writing

var multiply = function (x,y) {
  return x * y
}

In your case, you have "function (){ alert('meee'); }" and you want to save it as a function to var foo.

var fn = "function (){ alert('meee'); }";
var foo = new Function("return ("+fn+")")();
foo();
// alerts "meee"

The difference between Function and eval is eval runs in the private scope, while Function runs in the global scope.

var x="haha", y="hehe";

function test () {
  var x=15, y=34;
  eval("alert('eval: ' + x + ', ' + y)");
  new Function("alert('Func: ' + x + ', ' + y)")();
} 

test();

// eval: 15, 34
// Func: haha, hehe

Don't try to run it in the console, you'll get a deceiving result (consoles use eval). Writing it in a <script> tag and loading it in the browser will give the true result.

According to MDC. Use:

var multiply = new Function("x", "y", "return x * y");
var theAnswer = multiply(7, 6);