Use a regular expression to validate Angular2 controls.

RegexValidators.ts

import { AbstractControl } from 'angular2/common';

export class RegexValidators {
  static pattern(pattern: RegExp) : (c: AbstractControl) => {[key: string]: any } {
    return (control: AbstractControl): { [key: string]: any } => {
      let v: string = control.value;
      return pattern.test(v) ? null : { "pattern": { "requiredPattern": `^${pattern}$`, "actualValue": v } };
    };
  }
}

The current Validators.patterns takes a string and wraps it like this:

let regex = new RegExp(`^${pattern}$`);

This code just passes the expression straight through. Ideally, this should be union typed in Angular2 to accept either a RegExp or a string.