Regex to Match Scientific Notation

This regex matches numbers written in scientific notation (also called exponential notation). Here is the token-by-token breakdown:

^ — Anchors the match at the start of the string.

-? — Matches an optional minus sign for negative numbers.

\d+ — Matches one or more digits for the integer part of the coefficient (the number before the exponent). At least one digit is required.

(?:.\d+)? — An optional non-capturing group that matches a decimal point followed by one or more digits. This allows both integer coefficients like '5e3' and decimal coefficients like '5.2e3'. The entire group is optional thanks to the trailing ?.

[eE] — A character class matching either a lowercase 'e' or uppercase 'E'. Both forms are standard in scientific notation. Programming languages typically accept either case.

[+-]? — An optional character class matching a plus or minus sign for the exponent. Positive exponents like 'e+3' and negative exponents like 'e-3' are both valid. When omitted, the exponent is assumed positive.

\d+ — Matches one or more digits for the exponent value.

$ — Anchors the match at the end of the string.

This pattern validates scientific notation as used in most programming languages and scientific calculators. Examples include 6.022e23 (Avogadro's number), 1.6E-19 (electron charge), and -2.5e4. The pattern ensures a properly formed number with a valid exponent.