ngx-validation/src/app/directives/equal-validator.directive.ts

angular two and above validation directives by ReactiveCore

import { Directive, forwardRef, Attribute } from '@angular/core';
import { Validator, AbstractControl, NG_VALIDATORS } from '@angular/forms';

@Directive({
  selector: '[validateEqual][formControlName],' +
  '[validateEqual][formControl],[validateEqual][ngModel]',
  providers: [
    {provide: NG_VALIDATORS, useExisting: forwardRef(() => EqualValidator), multi: true}
  ]
})
export class EqualValidator implements Validator {
  constructor(@Attribute('validateEqual') public validateEqual: string,
              @Attribute('reverse') public reverse: string) {
  }

  private get isReverse(): boolean {
    if (!this.reverse) {
      return false;
    }
    return this.reverse === 'true' ? true : false;
  }

  validate(c: AbstractControl): {[key: string]: any} {
    // self value
    let v = c.value;

    // control value
    let e = c.root.get(this.validateEqual);

    // value not equal
    if (e && e.value !== '' && v !== e.value && !this.isReverse) {
      return {
        validateEqual: 'not equal'
      };
    }

    // value equal and reverse
    if (e && v === e.value && this.isReverse) {
      delete e.errors['validateEqual'];
      if (!Object.keys(e.errors).length) {
        e.setErrors(null);
      }
    }

    // value not equal and reverse
    if (e && v !== e.value && this.isReverse) {
      e.setErrors({validateEqual: false});
    }

    return null;
  }
}