Catch a referenceError in js

Question

I have a textarea where user can enter javascript code which upon press of the button would be passed to eval().

I am having trouble catching the referenceError for cases when a user enters something like this:

var myName = Maria;

instead of

var myName = "Maria";

Thank you for you time!

@sᴜʀᴇsʜᴀᴛᴛᴀ _user can enter javascript code which upon press of the button would be **passed to eval()**._ — Grundy, Sep 12 '15 at 09:31
You need to be **VERY CAREFUL** with `eval()` and executing user code in the browser, please make sure you know what you're doing before using anything like this in production — hammus, Sep 12 '15 at 09:31
You have misunderstood me - user does not just enter the name, but the entire js line i.e. var myName = ... which then gets executed in js via eval(), so user can pass anything. So when a user forgets quotes around the string, js throws referenceError which i need to catch because I want to code to continue running and give user feedback. — jacobdo, Sep 12 '15 at 09:32
For those concerned, I am well aware of the risks related to eval() — jacobdo, Sep 12 '15 at 09:33

score 29 · Accepted Answer · edited Oct 04 '18 at 20:07

29

Ok, as you said you understood the pit's of eval(), here i'm proposing a solution.

try {
    var myName = Maria;
} catch (e) {
    if (e instanceof ReferenceError) {
        // Handle error as necessary
    }
}

edited Oct 04 '18 at 20:07

Community

answered Sep 12 '15 at 09:36

Suresh Atta

score 7 · Answer 2 · answered Sep 12 '15 at 09:32

7

Try putting a try/catch block around the eval() call. Like this:

try {
    eval(userInput);
} catch (e) {
    // do something
}

(Note that passing user input to eval() is NOT something you should do on a real site, for security reasons.)

answered Sep 12 '15 at 09:32

ecraig12345

2 Answers2