Is there a difference in performance while doing null checks in below 2 ways -
if (!someObject) {
// dosomething
}
vs
if (someObject != null) {
// dosomething
}
-
If your question is about performance, why don't you just measure it?trincot– trincot2017-02-17 20:37:01 +00:00Commented Feb 17, 2017 at 20:37
-
@Yousuf Read github.com/rwaldron/idiomatic.js at "4.Conditional Evaluation"wf9a5m75– wf9a5m752017-02-17 20:39:05 +00:00Commented Feb 17, 2017 at 20:39
-
@wf9a5m75 Thanks for the link, looks like a good resource.Yousuf– Yousuf2017-02-17 20:49:25 +00:00Commented Feb 17, 2017 at 20:49
Add a comment
|
2 Answers
!someObject checks for all falsy values.
Not ( empty string, undefined, null, 0, false) - will all pass the condition
where as the first condition only checks for null.
if (someObject !== null) {
console.log('falsey');
}
someObject = null; // no message in console
someObject = ''; // falsey
someObject = undefined; // falsey
someObject = 0; // falsey
someObject = false; // falsey
Falsey check
if (!someObject) {
console.log('falsey');
}
someObject = null; // no message in console
someObject = ''; // no message in console
someObject = undefined; // no message in console
someObject = 0; // no message in console
someObject = false; // no message in console
5 Comments
Yousuf
Since !someObject is evaluating all truthy values, does it mean it is not as efficient when I need to check only for null's?
Sushanth --
Since it is just a simple check, the performance with be negligible for both the cases,
Yousuf
okay, I thought so. My colleague told me it is not efficient, so I was wondering.
alan
@Yousuf Your colleague's concern was probably more a combination of performance as well as your dependence on implicit typecasting to evaluate for a null or undefined value. (I am your colleague)
Mirko Vukušić
BTW, Benchmark.js says it's about 16% difference (Chrome,
someObject = {}). As long as someObject is not null. In case it's null, second option is faster: jsbench.me/tiizafwdy4to properly check for a null you'd have to write:
if(!someobject && typeof someobject!== "object")
Ideally typeof null should not return "object"
The Types and Grammar chapter in You Don't Know JS mentions:
this original bug in JS has persisted for nearly two decades, and will likely never be fixed because there’s so much existing web content that relies on its buggy behavior that “fixing” the bug would create more “bugs” and break a lot of web software.
Comments
