var name = "someName";
if(name !=null) {
// do something
}
- I am right now using http://underscorejs.org/#isNull, how would i do
the same using
underscore.js - Does it give any slight improvement in terms of performance for such functions.
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4 Answers
In underscore, you can use
if(!_.isNull(name)) {}
and in plain Javascript, you should use
if(name !== null) {}
You should avoid the loose inequality operator != because it does type coercion and undefined != null will return false.
Using plain Javascript is slightly faster because it doesn't have to invoke a function, but it will be imperceptible and it should hardly be a consideration.
I don't have a strong preference either way as far as readability goes, but it seems a little excessive and verbose to call a library function for such a simple check.
Comments
In underscore.js you must write this to achieve that functionality.
var name = "someName";
if(!(_.isNull(name ))) {
// do something
}
In underscore.js function isNull is written like this
_.isNull = function(obj) {
return obj === null;
};
So the difference is using == in your code and === in underscore.js.For more details about that difference you can look in this question.
Which equals operator (== vs ===) should be used in JavaScript comparisons?
P.S. I will suggest to write your own condition instead of using any library in such simple place.
var name = "someName";
if(name !== null)) {
// do something
}
2 Comments
Niet the Dark Absol
-1 for only mentioning the extreme simplicity of just writing
=== null. Yes, I just downvoted Chuck Norris.
Chuck Norris
The greatest mistake of your life :D
Well your original code is flawed because if name is an empty string, false, the number 0 or any other falsy value then it will be considered null as far as your test is concerned.
As a general rule, calling ANY function is an overhead that should be avoided if possible. In this case, calling a function just to test if a value is null, when you could very easily just write if( name === null), is just stupid, IMO...
answered May 25, 2012 at 8:30
Niet the Dark Absol
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2 Comments
XIU
Just for people that are going to come to this question, no "", false and 0 will not match null, only undefined and null will match null when using == null. On the other side, when checking for == false (or !something) THEN it'll also match null, undefined, 0, "", "0" and "false"
wchargin
@XIU Thank you.
"0" == false is always the one that gets me. What a crock…if ((!(_.isUndefined(data)) || _.isEmpty(data))) {
//Valid Data
}else {//Not Valid}
2 Comments
Shawn
Please elaborate on your answer.
Ashutosh Soni
Hi Shawn In case we need to perform some operation on json data /object so we can simple user he underscore library and perform 2 check first isUndefined (data) must be false and Is empty data is also valid so we jusy put condition for verify if ( !(_.isUndefined(data)) || _.isEmpty(data) ) { //Valid Data json data //TODO WORK } else { //Not Valid json result }