jquery - Javascript str.search("?") returns Unexpected Quantifier error - Stack Overflow

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I am able to search a string using str.search("me"); and str.search("=");

But when i serach for str.search("?");

I get the error Unexpected Quantifier.

Why is that? How can i search for "?" using something other than a regular expression?

I am able to search a string using str.search("me"); and str.search("=");

But when i serach for str.search("?");

I get the error Unexpected Quantifier.

Why is that? How can i search for "?" using something other than a regular expression?

• javascript
• jquery

Share Improve this question Follow edited Jul 31, 2011 at 0:30 karim79 343k6767 gold badges419419 silver badges407407 bronze badges asked Jul 29, 2011 at 19:49 zodzod 12.4k2525 gold badges7373 silver badges107107 bronze badges

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4 Answers 4

Sorted by: Reset to default 6

"?" is a special character in a regular expression (one of the "quantifiers") which means "match the preceding zero or one times". It lead to the error in this case because it was preceded by nothing. However, "a?" wouldn't have thrown an exception, but would match "b" so this is an important thing to look out for.

If using String.search, which takes a regular expression (as karim79 points out, it isn't the only way), use "[?]" or "\\?" or /\?/. These forms will prevent the "?" from being treated as a special regular expression construct.

Happy coding.

alert(str.indexOf("?")); // returns position as integer if present, -1 otherwise

Typical usage scenario is:

if(str.indexOf("?") !== -1) {
    // present
}

https://developer.mozilla/en/JavaScript/Reference/Global_Objects/String/indexOf

Try this:

alert(str.search("\\?"));

It is quantifier and you can`t directly use it. From javascriptkit.

? is short for {0,1}. Matches zero or one time.

and MSDN

? Matches the preceding character or subexpression zero or one time. For example, 'do(es)?' matches the "do" in "do" or "does". ? is equivalent to {0,1}

This is the right usage:

str.search("\\?")

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