Regex - any alphabet except "e"

Question

I want to make a regular expression for any alphabets except "e" This is what I came up with -

/([a-d]|[f-z])+?/i

• The above regex doesn't match "e" which is good.
• It matches for "amrica"
• But it also match "america" but it shouldn't because of the "e" in america

What am I doing wrong?

Answer 1

You may use [a-z] character class, but restrict it with a negative lookahead (?!e), group this pattern with a grouping construct (?:...) and add the anchors around the pattern:

/^(?:(?!e)[a-z])+$/i

See the regex demo.

This technique will work in all regex flavors that support lookaheads. Note in Java and some other languages, you may use character class subtraction, but it is not supported by JS RegExp (nor by Python re). E.g., in Java, you could use s.matches("(?i)[a-z&&[^e]]+").

Pattern details:

• ^ - start of string
• (?:(?!e)[a-z])+ - 1 or more characters from a-z and A-Z range BUT e and E
• $ - end of string anchor
• i - case insensitive modifier.

JS demo:

var rx = /^(?:(?!e)[a-z])+$/i;
var strs = ['america','e', 'E', 'world','hello','welcome','board','know'];
for (var s of strs) {
  console.log(s, "=>", rx.test(s));
}