Strings in VBScript

As you learned in Chapter 5, VBScript can store any type of data in a variable. String data is anything VBScript cannot interpret as another data type, such as a number or a date. Strings are simply any combination of letters, numbers, spaces, symbols, punctuation, and so forth. Often times, VBScript might interpret data as different types. For example, 5/7/2003 could be treated as a date or as a string, because it qualifies as both. In those instances, VBScript will coerce the data into one type or the other, depending on what you're trying to do with the data. Coercion is an important concept, especially when dealing with strings. For more information, refer to "What Are Variables?" in Chapter 5.

In your scripts, you'll always include strings within double quotation marks, which is how you let VBScript know to treat data as a string. For example, all of the following are acceptable ways to assign string data to a variable.

Var = "Hello"

Var = ""Hello""

Var = "Hello, there"

Var = vSomeOtherStringVariable

The second example is worth special attention. Notice that two sets of double quotes were used: This method will cause the variable Var to contain a seven-character string that begins and ends with quotes. Use this technique of doubling-up on quote marks whenever you need to assign the quote character itself as a part of the string.

VBScript refers to any portion of a string as a substring. Given the string Hello, one possible substring would be ell and another would be ello. The substring ello has its own substrings, including llo and ell. VBScript provides a number of functions for working with substrings. For example, you might write a script that accepts a computer name. The user might type just the name, such as Server1, or he might include a UNC-style name, such as \\Server1. Using VBScript's substring functions, you can get just the substring you want.

A large number of VBScript's intrinsic functions are devoted to string manipulation, and I'll cover most of them in this chapter. As a quick reference, here's each one, in alphabetical order, along with a quick description of what each does.

• Asc(). Returns the ASCII code for any single character.

• Chr(). Given an ASCII code, returns the corresponding character.

• CStr(). Converts a variable to a string.

• Escape(). Encodes a string for proper transmission as part of an Internet URL, so that strings such as "Hello world" become "Hello%20world."

• FormatCurrency(). Accepts a currency value and returns a properly formatted string. For example, formats 45.67 as $45.67.

• FormatDateTime(). Returns a properly formatted date or time string. For example, formats 4/5/2003 as April 5, 2003.

• FormatNumber(). Returns a formatted number. For example, formats 1055774 as 1,055,774.00.

• FormatPercent(). Returns a formatted percentage. For example, formats .67 as 67%.

• InStr(). Returns the position at which a specified substring can be found within a specified string.

• InStrRev(). Same as InStr(), but starts its search at the end of the specified string rather than the beginning.

• LCase(). Returns a string converted to lowercase.

• Left(). Returns the specified leftmost characters of a specified string.

• Len(). Returns the length of a string.

• LTrim(). Trims spaces from the left end of a string.

• Mid(). Returns a substring from a specified string, starting with the specified beginning character and continuing for the specified length.

• Replace(). Replaces all instances of the specified substring with the specified replacement substring.

• Right(). Returns the specified rightmost characters of a specified string.

• RTrim(). Trims spaces from the right end of a string.

• Space(). Returns a string containing the specified number of spaces.

• StrComp(). Compares two strings and returns an appropriate value.

• StrReverse(). Reverses the specified string's characters, so that "Hello" would become "olleH."

• Trim(). Trims spaces from both ends of a string.

• UCase(). Returns a string with all characters converted to uppercase.

• Unescape(). Decodes a string encoded with the Escape() function.

You should realize that none of these functions change the contents of a string variable. For example, Var1 = Trim(Var2) does not change the contents of Var2. Instead, it trims all spaces from the left and right ends of Var2's contents, and assigns the result to Var1. If you want to change the contents of a variable, you can use something like Var1 = Trim(Var1). Internally, VBScript creates a new string to hold the result of the Trim() function, and then assigns that result back to the Var1 variable. This behind-the-scenes assignment is what actually changes the contents of Var1, not the Trim() function.