Check for empty of null in javascript

Question

I had a bug that turned out to be because I forgot to check for null values. I added the check, but would like if it could be written more concise.

<ListItem onClick={!pattern.capped && !pattern.hasInlineRef ? search(pattern.dbValue, pattern.dbValue === "" || pattern.dbValue === null) : undefined}>

Can this check for empty or null be shortened?

search(pattern.dbValue, pattern.dbValue === "" || pattern.dbValue === null)

It's written in Typescript, but I guess the curly braces make it JavaScript.

"It's written in Typescript, but I guess the curly braces make it JavaScript." all TypeScript compiles to JavaScript. At runtime, you only have JS running. — VLAZ
– VLAZ, Commented Sep 30, 2019 at 6:46
At least extract the dbValue property first, I think. If its only falsey values are the empty string and null, just call Boolean on it in the second argument — CertainPerformance
– CertainPerformance, Commented Sep 30, 2019 at 6:46
you can write some util function for that and use the function to get rid of long code. One more additional thing is undefined check — Kaushik
– Kaushik, Commented Sep 30, 2019 at 6:48

thortsx · Accepted Answer · 2019-09-30 06:56:38Z

2

First, you can create an util function to check null, empty or undefined:

export function isNullOrEmpty(value) {
    return (value === null || value === undefined || value === "") ? true : false 
}

Or, you can fast test with falsy and truthy:

search(pattern.dbValue, !pattern.dbValue)

List of falsy values in JavaScript: MDN Falsy

false
null
undefined
0
NaN
''
document.all

answered Sep 30, 2019 at 6:56

thortsx

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6 Comments

sshanzel Over a year ago

yup, it is a good practice to isolate a function one of few reasons is, easy testing.

Drew Reese Over a year ago

Equality checks are already truthy/falsy, just return value === null || value === undefined || value === "";, or because all those values are falsey values, just double-bang it, return !!value;. The only reason I can see for explicit checks is if 0 or NaN needed to be treated differently.

sshanzel Over a year ago

!value would be enough, yes.

Drew Reese Over a year ago

Edit went in same time as my comment. :)

VLAZ Over a year ago

@DrewReese but then that would also catch 0 which might be undesirable.

|

govardhan n · Accepted Answer · 2019-09-30 08:06:59Z

0

You can create an helper function in a separate folder and pull out this function into the files where you need to check for null, undefined, empty string or an empty object.You can write something like this:

export default value =>
value === undefined ||
value === null ||
(typeof value === 'object' && Object.keys(value).length === 0) ||
(typeof value === 'string' && value.trim().length === 0);

Hope this helps

answered Sep 30, 2019 at 8:06

govardhan n

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