JavaScript: indexOf vs. Match when Searching Strings?

Question

Readability aside, are there any discernable differences (performance perhaps) between using

str.indexOf("src")  

and

str.match(/src/) 

I personally prefer match (and regexp) but colleagues seem to go the other way. We were wondering if it mattered ...?

EDIT:

I should have said at the outset that this is for functions that will be doing partial plain-string matching (to pick up identifiers in class attributes for JQuery) rather than full regexp searches with wildcards etc.

class='redBorder DisablesGuiClass-2345-2d73-83hf-8293'  

So it's the difference between:

string.indexOf('DisablesGuiClass-'); 

and

string.match(/DisablesGuiClass-/) 

Answer 1

RegExp is indeed slower than indexOf (you can see it here), though normally this shouldn't be an issue. With RegExp, you also have to make sure the string is properly escaped, which is an extra thing to think about.

Both of those issues aside, if two tools do exactly what you need them to, why not choose the simpler one?

Answer 2

Your comparison may not be entirely fair. indexOf is used with plain strings and is therefore very fast; match takes a regular expression - of course it may be slower in comparison, but if you want to do a regex match, you won't get far with indexOf. On the other hand, regular expression engines can be optimized, and have been improving in performance in the last years.

In your case, where you're looking for a verbatim string, indexOf should be sufficient. There is still one application for regexes, though: If you need to match entire words and want to avoid matching substrings, then regular expressions give you "word boundary anchors". For example:

indexOf('bar') 

will find bar three times in bar, fubar, barmy, whereas

match(/\bbar\b/) 

will only match bar when it is not part of a longer word.

As you can see in the comments, some comparisons have been done that show that a regex may be faster than indexOf - if it's performance-critical, you may need to profile your code.