Regular Expressions 101

^start of line

\s*any whitespace character, repeated any number of times

Character Class[0-9]*

*matches any number of characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Group 1([a-zA-Z]+[0-9]*)+

+repeats the group contents below at least once:

Character Class[a-zA-Z]+

+matches at least one character from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Character Class[0-9]*

*matches any number of characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Group 2( *\+ *[0-9]*([a-zA-Z]{1,2}[0-9]*))*

*repeats the group contents below any number of times:

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

\+the literal + (43₁₀ / 53₈ / 2B₁₆)

*the literal (32₁₀ / 40₈ / 20₁₆) , repeated any number of times

Character Class[0-9]*

*matches any number of characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

Group 3([a-zA-Z]{1,2}[0-9]*)

Character Class[a-zA-Z]{1,2}

{1,2}matches between 1 and 2 characters from the set below:

a-zone character from a (97₁₀) to z (122₁₀) (case sensitive)

A-Zone character from A (65₁₀) to Z (90₁₀) (case sensitive)

Character Class[0-9]*

*matches any number of characters from the set below:

0-9one character from 0 (48₁₀) to 9 (57₁₀)

\s*any whitespace character, repeated any number of times

$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.

Search reference

Regular Expression

^\s*[0-9]* *([a-zA-Z]+[0-9]*)+( *\+ *[0-9]*([a-zA-Z]{1,2}[0-9]*))*\s*$

A + B
2H2 + O2
2H2O
C + O2
2H2O 
 2H2O
 2H2O