VBScript InStr Function

The InStr function returns the position of the first occurrence of one string within another.
The InStr function can return the following values:

• If string1 is "" - InStr returns 0
• If string1 is Null - InStr returns Null
• If string2 is "" - InStr returns start
• If string2 is Null - InStr returns Null
• If string2 is not found - InStr returns 0
• If string2 is found within string1 - InStr returns the position at which match is found
• If start > Len(string1) - InStr returns 0

Tip: Also look at the InStrRev function

Syntax

InStr([start,]string1,string2[,compare])

Parameter	Description
start	Optional. Specifies the starting position for each search. The search begins at the first character position (1) by default. This parameter is required if compare is specified
string1	Required. The string to be searched
string2	Required. The string expression to search for
compare	Optional. Specifies the string comparison to use. Default is 0Can have one of the following values: 0 = vbBinaryCompare - Perform a binary comparison 1 = vbTextCompare - Perform a textual comparison

Example 1:
<script type="text/vbscript">

txt="This is a beautiful day!"
document.write(InStr(txt,"beautiful"))

</script>

The output of the code above will be:
11

Example 2:
Finding the letter "i", using different starting positions:

<script type="text/vbscript">

txt="This is a beautiful day!"
document.write(InStr(1,txt,"i") & "<br />")
document.write(InStr(7,txt,"i") & "<br />")

</script>

The output of the code above will be:
3
16

Example 3:

Finding the letter "t", with textual, and binary, comparison:

<script type="text/vbscript">

txt="This is a beautiful day!"
document.write(InStr(1,txt,"t",1) & "<br />")
document.write(InStr(1,txt,"t",0) & "<br />")

</script>

The output of the code above will be:
1
15
 

VBScript InStrRev Function:

The InStrRev function returns the position of the first occurrence of one string within another. The search begins from the end of string, but the position returned counts from the beginning of the string.
The InStrRev function can return the following values:

• If string1 is "" - InStrRev returns 0
• If string1 is Null - InStrRev returns Null
• If string2 is "" - InStrRev returns start
• If string2 is Null - InStrRev returns Null
• If string2 is not found - InStrRev returns 0
• If string2 is found within string1 - InStrRev returns the position at which match is found
• If start > Len(string1) - InStrRev returns 0

Tip: Also look at the InStr function

Syntax

InStrRev(string1,string2[,start[,compare]])

Parameter	Description
string1	Required. The string to be searched
string2	Required. The string expression to search for
start	Optional. Specifies the starting position for each search. The search begins at the last character position by default (-1)
compare	Optional. Specifies the string comparison to use. Default is 0Can have one of the following values: 0 = vbBinaryCompare - Perform a binary comparison 1 = vbTextCompare - Perform a textual comparison

Examples

Example 1

<script type="text/vbscript">

txt="This is a beautiful day!"
document.write(InStrRev(txt,"beautiful"))

</script>

The output of the code above will be:
11

Example 2
Finding the letter "i", using different starting positions:
<script type="text/vbscript">

txt="This is a beautiful day!"
document.write(InStrRev(txt,"i",-1) & "<br />")
document.write(InStrRev(txt,"i",7) & "<br />")

</script>

The output of the code above will be:
16
6


Example 3
Finding the letter "T", with textual, and binary, comparison:
<script type="text/vbscript">

txt="This is a beautiful day!"
document.write(InStrRev(txt,"T",-1,1) & "<br />")
document.write(InStrRev(txt,"T",-1,0) & "<br />")

</script>

The output of the code above will be:
15
1