Question

I’m doing a pretty basic string matching test as follows:

if(msList.indexOf(textChoice) != -1)

This works well except that occasionally the sub-string I’m looking for (textChoice) ends with an asterisk. Then I end up getting false matches because the asterisk in the string is interpreted as an operator, not a character in the string.

So how can I do this test so that any asterisks in the sub-string are treated as regular characters?

PS. I know the simple answer is “Don’t include asterisks in your sub-string” but they’re in the data I’m working with–I can’t get rid of them.

Answer 1

All characters in the substring will be treated as regular characters. * is not a special operator and does not change the behavior of indexOf in any way. Moreover, the indexOf method should never return false. It will return:

• -1 if no match is found or
• starting index of matching substring if found

Note that the starting index can be 0 which does not equate to false for substring searching. It just means that the substring was found in the beginning of the string.

"ABC".indexOf("AB") // 0

Put explicit checks comparing the return value with -1 instead of just checking for a truthy value.

if("ABC".indexOf("AB")) {
    // will never execute
}

Instead, always do this:

if("ABC".indexOf("AB") != -1) {
   // ..
}