How can I execute Javascript stored as a string?

Question

Hi there!

How do I execute some Javascript that is a string?

function ExecuteJavascriptString()
{
    var s = "alert('hello')";
    // how do I get a browser to alert('hello')?
}

Many thanks!

Answer 1

The eval function will evaluate a string that is passed to it.

But the use of eval can be dangerous, so use with caution.

Edit: annakata has a good point -- Not only is eval dangerous, it is slow. This is because the code to be evaluated must be parsed on the spot, so that will take some computing resources.

Answer 2

Use eval().

W3C documentation on eval.

You will probably get a lot of warnings about using this safely. do NOT allow users to inject ANYTHING into eval() as it is a huge security issue.

You'll also want to know that eval() has a different scope.

Answer 3

eval should do it.

eval(s);

Answer 4

eval(s);

But this can be dangerous if you are taking data from users, although I suppose if they crash their own browser thats their problem.

Answer 5

eval(s);

Remember though, that eval is very powerful and quite unsafe. You better be confident that the script you are executing is safe and unmutable by users.

Answer 6

With eval(). See:

http://www.devguru.com/Technologies/ecmascript/quickref/eval.html

Answer 7

Use eval as below. Eval should be used with caution, a simple search about "eval is evil" should throw some pointers.

function ExecuteJavascriptString()
{
    var s = "alert('hello')";
    eval(s);
}

Answer 8

but is there any way to actually avoid eval() to the previous example?

Answer 9

try this:

  var script = "<script type=\"text/javascript\"> content </script>";
  //using jquery next
  $('body').append(script);//incorporates and executes inmediatelly
  //personally i didnt test it. but seems to work.

good look;