On every site that talks about VBScript, the '&' operator is listed as the string concatenation operator. However, in some code that I have recently inherited, I see the '+' operator being used and I am not seeing any errors as a result of this. Is this an accepted alternative?
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4 Answers
The & operator does string concatenation, that is, forces operands to be converted to strings (like calling CStr on them first). +, in its turn, forces addition if one of the expressions is numeric. For example:
1 & 2
gives you 12, whereas
1 + 2
"1" + 2
1 + "2"
give you 3.
So, it is recommended to use & for string concatenation since it eliminates ambiguity.
1 Comment
baacke
+1 for specifying string number + number. Accepted answer doesn't mention vbscript converting numeric strings to numbers.
The + operator is overloaded, whereas the & operator is not. The & operator only does string concatenation. In some circles the & operator is used as a best practice because it is unambiguous, and therefore cannot have any unintended effects as a result of the overloading.
3 Comments
Wolf
The + operator is overloaded -- overloaded in what sense?
Robert Harvey
@wolf in VB the + operator can do both addition and concatenation, depending on context.
Wolf
Well, I already read this. I found the word overloaded itself so overloaded that I wished, the answer could be a little bit more precise in this point.
+ operator might backfire when strings can be interpreted as numbers. If you don't want nasty surprises use & to concatenate strings.
Comments
In some cases the + will throw an exception; for example the following:
Sub SimpleObject_FloatPropertyChanging(fvalue, cancel)
'fvalue is a floating point number
MsgBox "Received Event: " + fvalue
End Sub
You will get an exception when the COM object source fires the event - you must do either of the following:
MsgBox "Received Event: " & fvalue
or
MsgBox "Received Event: " + CStr(fvalue)
It may be best in either case to use CStr(value); but using & per above comments for string concatenation is almost always best practice.
