Of course, for a small number of string connections, efficiency doesn't have much impact on the program, so let's consider an extreme problem: connecting all numbers from 1 to 100000 to a string.
The simplest solution is to use the & connection directly:
Copy Code code as follows:
Begin = Timer
For i = 1 to 100000
str = str & CSTR (i)
Next
WScript.Echo Str
finish = Timer
WScript.Echo Finish-begin
But this program on my computer needs to run for 60.648 seconds, inefficient. To change a scheme, use an array to resolve:
Copy Code code as follows:
Begin = Timer
Dim arr (100000)
For i = 1 to 100000
Arr (i) = i
Next
str = Join (arr, "")
WScript.Echo Str
finish = Timer
WScript.Echo Finish-begin
This time it took only 0.742 seconds, about 60 times times faster. In this problem the size of the array can be determined beforehand, and a dynamic array must be used if the size of the array cannot be predicted. I'm low level, not using a dynamic array, is there a simpler way? The answer is yes, that's the dictionary:
Copy Code code as follows:
Begin = Timer
Set Odic = CreateObject ("Scripting.Dictionary")
For i = 1 to 100000
Odic.add I, CStr (i)
Next
str = Join (Odic.items, "")
WScript.Echo Str
finish = Timer
WScript.Echo Finish-begin
The elapsed time is 1.593, twice times that of the array, but it is much faster than & and is easier to use than arrays.
Summarizing the:& join symbol is relatively inefficient and can be used when connecting to a small number of strings, but you should use the Join function + array when connecting a large number of strings.
Original: http://demon.tw/programming/vbs-string-concatenation.html
