Can I run a JavaScript in JavaScript?

Question

Possible Duplicate:
Is It Possible to Sandbox JavaScript Running In the Browser?

I would like to give the user the ability to input JavaScript in a textarea like this:

<!DOCTYPE html>
  <html>
    <head>
      <script>
        function lapzwans()
        {
          var d = document.getElementById("area").value;
          document.getElementById("blahblah").innerHTML = d;
        }
      </script>
    </head>
  <body>
    <h1>Javascript in Javascript</h1>
    <p>This experiment attempts to launch a script from another script.</p>
    <p>Enter your script in the text area</p>
    <textarea type="text" id="area"></textarea>
    <button onclick="lapzwans()">Click here</button>
    <p id="blahblah"></p>
    <p id="deegroller">Make this text green</p>
  </body>
</html>

I have tried this, but I get no result.
Is it impossible to do this, or am I doing things wrong?
Thanks in advance.

Use an eval() function to run a javascript code, instead of just placing it as a plain text — deb0rian, Nov 02 '12 at 00:31
A dangerous habit question was asked. And with JavaScript, you can run any code you want in console, without eval being used by the owner.. — deb0rian, Nov 02 '12 at 00:36
@Daedalus `eval()` is an actual answer. Dangerous or not, for this question, it's an answer. — Whymarrh, Nov 02 '12 at 00:36

score 1 · Answer 1 · answered Nov 02 '12 at 00:38

1

the eval method takes whatever string is passed to it and tries to run it.

eval("alert('foo')");

will alert "foo";

answered Nov 02 '12 at 00:38

Yevgeny Simkin

27,946
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score 1 · Answer 2 · answered Nov 02 '12 at 00:40

1

You don't need to use the evil eval to do this.

function lapzwans()
{
       var d=document.getElementById("area").value;
       document.getElementById("blahblah").innerHTML=d;

       var userScript = new Function(d);
       userScript();
}

answered Nov 02 '12 at 00:40

Reza Assar

209
1
6

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How is this for any practical purposes different from `eval()`? – millimoose Nov 02 '12 at 00:55
It's not at all, there's nothing wrong with showing someone two wrong ways to do something though. – Reza Assar Nov 02 '12 at 01:51
1

There's nothing wrong with that. I was objecting to calling `eval()` evil then doing the same basic thing. – millimoose Nov 02 '12 at 02:17
1

Calling eval evil was sarcastic. His question is the definition of eval. As an example ("Don't kill him, murder him instead"). – Reza Assar Nov 02 '12 at 04:36
Thanks but this does not work form me. However evil eval works fine. – David Leegwater Nov 02 '12 at 13:40

score 1 · Accepted Answer · edited May 23 '17 at 10:25

1

One possible answer:

eval(/* some JS here */);

Note though that what you are trying to do can be dangerous (in some cases) as you are allowing user-written arbitrary JS to be executed.

Can I run a JavaScript in JavaScript?

3 Answers3