@buka/class-transformer-extra/dist/esm/src/string/trim.js

class-transformer-extra contains methods that's aren't included in the class-transform package.

import { Transform } from 'class-transformer';
export function Trim() {
    return Transform(function TrimTransform({ value }) {
        return (typeof value === 'string' ? value.trim() : value);
    });
}