How to check if a variable is not null?
Solution 1:
They are not equivalent. The first will execute the block following the if
statement if myVar
is truthy (i.e. evaluates to true
in a conditional), while the second will execute the block if myVar
is any value other than null
.
The only values that are not truthy in JavaScript are the following (a.k.a. falsy values):
null
undefined
0
-
""
(the empty string) false
NaN
Solution 2:
Here is how you can test if a variable is not NULL:
if (myVar !== null) {...}
the block will be executed if myVar is not null.. it will be executed if myVar is undefined or false or 0
or NaN
or anything else..
Solution 3:
Have a read at this post: http://enterprisejquery.com/2010/10/how-good-c-habits-can-encourage-bad-javascript-habits-part-2/
It has some nice tips for JavaScript in general but one thing it does mention is that you should check for null like:
if(myvar) { }
It also mentions what's considered 'falsey' that you might not realise.