Avoid an error from an undefined input-field in javascript

Question

I have an input-field in my form which sometimes gets displayed and sometimes not. When the input-field doesn´t get displayed and the form is about to get sent the script throws an error:

Cannot read property 'value' of undefined

I tried to catch that with this code:

if (typeof document.forms["add-new-job"].addjob_companyselect.value !== 'undefined') {
        // do something
}

But the same error comes again on this line. How can I skip an undefined field?

Maybe just check to see if it's defined first, before trying to extract its `.value`? (though this sounds like a bit of an X/Y problem) — CertainPerformance, Feb 19 '19 at 22:41
You'll want to check the `typeof document.forms["add-new-job"].addjob_companyselect`, not its `.value` — Bergi, Feb 19 '19 at 22:41
Check out this solution... [https://stackoverflow.com/questions/46700783/any-script-to-ignore-undefined-variable/46700934](https://stackoverflow.com/questions/46700783/any-script-to-ignore-undefined-variable/46700934) — mindmaster, Feb 19 '19 at 22:44

Tony Gentilcore · Accepted Answer · 2019-02-19T22:44:52.323

1

var addNewJobElement = document.forms["add-new-job"].addjob_companyselect;
if (addNewJobElement && addNewJobElement.value) {
    // do something
}

edited Feb 19 '19 at 22:44

answered Feb 19 '19 at 22:41

Tony Gentilcore

193
1
11

An input's `.value` is never `undefined` – Bergi Feb 19 '19 at 22:42
Also, if the form doesn't exist yet, this will also throw. – CertainPerformance Feb 19 '19 at 22:42

Avoid an error from an undefined input-field in javascript

1 Answers1