regex to match entire words containing only certain characters

Question

I want to match entire words (or strings really) that containing only defined characters.

For example if the letters are d, o, g

Answer 1

Depending on the language, this should do what you need it to do. It will only match what you said above;

this regex:

[dog]+(?![\w,])

in a string of ..

dog god ogd, dogs o

will only match..

dog, god, and o

Example in javascript

Example in php

Anything between two [](brackets) is a character class.. it will match any character between the brackets. You can also use ranges.. [0-9], [a-z], etc, but it will only match 1 character. The + and * are quantifiers.. the + searches for 1 or more characters, while the * searches for zero or more characters. You can specify an explicit character range with curly brackets({}), putting a digit or multiple digits in-between: {2} will match only 2 characters, while {1,3} will match 1 or 3.

Anything between () parenthesis can be used for callbacks, say you want to return or use the values returned as replacements in the string. The ?! is a negative lookahead, it won't match the character class after it, in order to ensure that strings with the characters are not matched when the characters are present.