Google on “scientific notation regexp” shows a number of matches, including this one (don’t use it!!!!) which uses
*** warning: questionable ***
/[-+]?[0-9]*\.?[0-9]+([eE][-+]?[0-9]+)?/
which includes cases such as -.5e7 and +00000e33 (both of which you may not want to allow).
Instead, I would highly recommend you use the syntax on Doug Crockford’s JSON website which explicitly documents what constitutes a number in JSON. Here’s the corresponding syntax diagram taken from that page:
(source: json.org)
If you look at line 456 of his json2.js script (safe conversion to/from JSON in javascript), you’ll see this portion of a regexp:
/-?\d+(?:\.\d*)?(?:[eE][+\-]?\d+)?/
which, ironically, doesn’t match his syntax diagram…. (looks like I should file a bug) I believe a regexp that does implement that syntax diagram is this one:
/-?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+\-]?\d+)?/
and if you want to allow an initial + as well, you get:
/[+\-]?(?:0|[1-9]\d*)(?:\.\d+)?(?:[eE][+\-]?\d+)?/
Add capturing parentheses to your liking.
I would also highly recommend you flesh out a bunch of test cases, to ensure you include those possibilities you want to include (or not include), such as:
allowed:
+3
3.2e23
-4.70e+9
-.2E-4
-7.6603
not allowed:
+0003 (leading zeros)
37.e88 (dot before the e)
Good luck!