StatelessRegExp.js

class StatelessRegExp extends RegExp {

  * exec(str, index = 0) {
    let lastIndex = this.lastIndex = index;

    let match;
    while ((match = super.exec(str)) !== null) {
      lastIndex = this.lastIndex;
      yield match;
      this.lastIndex = lastIndex;
    }
  }

  * test(str, index = 0) {
    let lastIndex = this.lastIndex = index;

    let test;
    while ((test = super.test(str)) !== null) {
      lastIndex = this.lastIndex;
      yield test;
      this.lastIndex = lastIndex;
    }
  }
}