Regular Expressions 101

Explanation
Pro

^start of line

-?optionally matches the literal - (45₁₀ / 55₈ / 2D₁₆)

\d+a digit, repeated at least once

\.?optionally matches the literal . (46₁₀ / 56₈ / 2E₁₆)

Group 1(\d+)?

?repeats the group contents below at most once:

\d+a digit, repeated at least once

Group 2([eE][+-]?\d+)?

?repeats the group contents below at most once:

Character Class[eE]

ethe literal e (101₁₀ / 145₈ / 65₁₆) (case sensitive)

Ethe literal E (69₁₀ / 105₈ / 45₁₆) (case sensitive)

Character Class[+-]?

?matches at most one character from the set below:

+the literal + (43₁₀ / 53₈ / 2B₁₆)

-the literal - (45₁₀ / 55₈ / 2D₁₆)

\d+a digit, repeated at least once

$end of line

Global pattern flags

g modifier: global. Finds all matches instead of stopping after the first

m modifier: multiline. Causes ^ and $ to match the start and end of each line, not only the start and end of the string

Detailed match information will be displayed here automatically.

26 tokens

^-?\d+\.?(\d+)?([eE][+-]?\d+)?$

42
-42
4.2
-4.2
4.2e9
4.2e+9
4.2e-9
-4.2e9
-4.2e+9
-4.2e-9
0.666
-0.666

42
-42
4.2
-4.2
4.2e9
4.2e+9
4.2e-9
-4.2e9
-4.2e+9
-4.2e-9
0.666
-0.666