正则表达式可删除除字母和 '[单引号] 之外的任何内容

Question

How can I change this regular expression to remove everything from a string except alphabets and a '(single quote)?

pattern = /\b(ma?c)?([a-z]+)/ig;

1. this pattern removes unwanted spaces and capitalizes the first letter and turns the rest into lower case
2. By alphabets I mean English letters az.

Answer 1

To remove characters, you'd need to use something that actually does that, like the string replace function (which can accept a regular expression as the "from" parameter).

Then you're just dealing with a normal application of a character class , which in JavaScript (and most other regular expression variants) is described using [...] , where ... is what should be in the class. You'd use the ^ at the beginning to invert the meaning of the class:

In your case, it might be:

str = str.replace(/[^A-Za-z']/g, "");

...which will replace except the English characters AZ (ABCDEFGHIJKLMNOPQRSTUVWXYZ), az (abcdefghijklmnopqrstuvwxyz), and the single quote with nothing (eg, remove it).

 let str = "This is a test with the numbers 123 and a '."; console.log("before:", str); str = str.replace(/[^A-Za-z']/g, ""); console.log("after: ", str);

However , note that alphabetic characters not used in English will not be excepted, and there are a lot of those in the various languages used on the web (and even, perversely, in English, in "borrowed" words like "voilà" and "naïve").

You've said you're okay with just English AZ, but for others coming to this: In environemnts supporting ES2018 and above's Unicode property matching , you could handle anything considered "alphabetic" by Unicode instead of just AZ by using the \\p{Alpha} property. The \\p means "matching this Unicode property" (as usual, the lowercase version \\p means "matching" and the uppercase version \\P means "not matching") and the {Alpha} means "alphabetic":

str = str.replace(/[^\p{Alpha}']/gu, "");

(Note that, again, \\p{Alpha} means "alphabetic" but because it's in a negated character class, we're excluding alphabetic characters.)

Note the u flag on that, to enable newer Unicode features. That handles the "voilà" and "naïve" examples too:

 let str = "This is a test with the numbers 123 and a ' and voilà and naïve."; console.log("before:", str); str = str.replace(/[^\\p{Alpha}']/gu, ""); console.log("after: ", str);