JavaScript RegExp: Different results: Built pattern using string & using regexp “literal”?

Question

Is there any differences between using RegExp literals vs strings?

http://jsfiddle.net/yMMrk/

String.prototype.lastIndexOf = function(pattern) {
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Answer 1

Generally speaking, if you use a string to construct a regex, you need to escape backslashes; if you use a regex literal, you need to escape slashes if they occur in your regex.

So the regex

\s/

can be written as a JavaScript string like this:

"\\s/"

and as a JavaScript regex literal like this:

/\s\//

Also, there is a difference in the handling of mode modifiers. For example, to make a regex case-insensitive, you can construct a regex object from a JavaScript string like this:

var myre = new RegExp("[a-z]", "i");

With a regex literal, you can do that directly:

var myre = /[a-z]/i;

Also, see this tutorial.