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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!

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!

• javascript
• referenceerror

Share Improve this question Follow asked Sep 12, 2015 at 9:27 jacobdojacobdo 1,61544 gold badges1616 silver badges3434 bronze badges 7

• An user entered value is always a string. – Suresh Atta Commented Sep 12, 2015 at 9:28
• @sᴜʀᴇsʜᴀᴛᴛᴀ user can enter javascript code which upon press of the button would be passed to eval(). – Grundy Commented Sep 12, 2015 at 9:31
• 1 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 Commented Sep 12, 2015 at 9:31
• 1 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 Commented Sep 12, 2015 at 9:32
• For those concerned, I am well aware of the risks related to eval() – jacobdo Commented Sep 12, 2015 at 9:33

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2 Answers 2

Sorted by: Reset to default 30

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
    }
}

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.)

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