While using an ‘if’ statement to check whether a variable is an empty string or not we can write it in two ways i.e. if(” == $variable) and if($variable == ”). I want to know what is the impact of above in different cases?
Thanks in advance!!
7
In a modern language, you should be writing your conditions of the form if($variable == ""). This makes the condition easier to read for natural English speakers.
In a legacy language, it sometimes was considered good practice to use the form if("" == $variable) as if you used the more natural form it was possible to create compilable and runnable code which was bugged if you accidentally missed one of the ‘=’ symbols.
Now, most compilers, even for these older languages, will at least warn you if you accidentally miss the ‘=’ symbol.
TL;DR; – use if($variable == "")
4
This highly depends on the language used!
If == is implemented as a method in an object oriented language then the construct if ($variable == "") could lead to an exception because the object ($variable) might not be initialized or even null.
If you reverse the expression (if ("" == $variable)) then you can be sure that the object acted on ("" is always initialized and never null).
As an example in Java (where the method is called .equals()):
string.equals("")
can cause a NullPointerException because the object string may be null.
"".equals(string)
cannot lead to a NullPointerException as the object "" is never null.
If == is not a method of an object then it does not matter which order is used.
I think that many programmers with such a background use the expression if ("" == $variable) because they are more familiar with it.
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