If statement run if empty string

Question

If I do this in the console:

document.querySelectorAll('.error')

An object of length 3 is returned.

If any of the property values are empty, then I do not want my if statement to run:

After getting frustrated with this (I was using != '') the internet told me to use !== ""

Here is the output for property in the object:

document.querySelectorAll('.error')[0]
""

document.querySelectorAll('.error')[1]
"some string"

document.querySelectorAll('.error')[2]
""

My newness to JS is probably apparent by my question so far. Is the "best" way to check for empty string to use what I have done !==?

<script>

var errorElems = document.querySelectorAll('.error');

for(i=0; i<errorElems.length; i++) {
    if(errorElems[i].textContent !== ""){
        dataLayer.push({
            "event": "errors",
            "eventCategory": "error messages",
            "eventAction": errorElems[i].id,
            "eventLabel": errorElems[i].textContent
            })
        };
    };

This appears to be working. But I'm one person checking in one browser (Chrome) on a desktop machine, if that matters.

What would be the most full proof (yet reasonably straightforwards) means to doing this? Is !== best test?

meskobalazs · Accepted Answer · 2014-12-24 17:00:05Z

3

If its an empty string, !== "" is the way to go. If it can be undefined too (as it very much can happen when selecting DOM elements), then you should make a check like this:

if (typeof string !== 'undefined' && string !== "")

answered Dec 24, 2014 at 17:00

meskobalazs

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Comments

Icepickle · Accepted Answer · 2014-12-24 17:02:19Z

1

empty values are parsed as false, if you just try

if (!errorElems[i].textContent) {
    ... // error handling code here
}

answered Dec 24, 2014 at 17:02

Icepickle

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1 Comment

Doug Fir Over a year ago

Thank you, this is helpful. Accepting the other answer for no other reason than timing.

Carlos Man · Accepted Answer · 2014-12-24 17:35:08Z

1

The Node.textContent property, as per its specification can return a null value, so it would be better to test it with something like this:

var errorElems = document.querySelectorAll('.error'),
    errorElem;

for (i=0; i < errorElems.length; i++) {
    errorElemText = errorElems[i].textContent;
    if (typeof errorElemText === "string" && errorElemText !== "") {
        dataLayer.push({
            "event": "errors",
            "eventCategory": "error messages",
            "eventAction": errorElems[i].id,
            "eventLabel": errorElemText
        });
    }
}

edited Dec 24, 2014 at 17:35

answered Dec 24, 2014 at 17:16

Carlos Man

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2 Comments

Doug Fir Over a year ago

thanks for the tip. So in that case could I not do: if (typeof errorElemText === "string" && errorElemText !== "") in a oner?

Carlos Man Over a year ago

Of course. My bad. I pieced it together quickly. I edited my answer accordingly.

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