how to add dash/hyphen in input field after 2 digits angular 4

Question

hey i want to add dashes when user enter date of birth manually. like this 08-18-2019 but i cannot be able to do this

 public dateOfBirth: { year: number; month: number; day: number };

html file

 <input
          ngbDatepicker
          dobMask
          #d="ngbDatepicker"
          #dobF="ngModel"
          class="form-control input-underline input-lg"
          id="dob"
          [(ngModel)]="dateOfBirth"
          placeholder="mm-dd-yyyy"
          name="dp"
          [ngClass]="{
            invalid:
              (dobF.value === null || isString(dobF.value) || futureDate) && dobF.touched
          }"
          required
        />

i tried directive but result is something like this 11---------3

here is my directive code

@Directive({
selector: '[dobMask]'
})
export class DobDirective {

@HostListener('input', ['$event'])
onKeyDown(event: KeyboardEvent) {
const input = event.target as HTMLInputElement;

let trimmed = input.value.replace(/\s+/g, '');
if (trimmed.length > 8) {
  trimmed = trimmed.substr(0, 8);
}

let numbers = [];
for (let i = 0; i < trimmed.length; i += 2) {
  numbers.push(trimmed.substr(i, 2));
}

input.value = numbers.join('-');

  }
}

this is what i am getting

my expected result is i.e 08-17-2019

can anyone help me how can i achieve that?

Answer 1

Modified your directive a little bit and its working fine

import {Directive,HostListener} from '@angular/core'

@Directive({
selector: '[dobMask]'
})
export class DobDirective {

@HostListener('input', ['$event'])
onKeyDown(event: KeyboardEvent) {
const input = event.target as HTMLInputElement;

let trimmed = input.value.replace(/\s+/g, '');

if (trimmed.length > 10) {
  trimmed = trimmed.substr(0, 10);
}


trimmed = trimmed.replace(/-/g,'');

 let numbers = [];
  numbers.push(trimmed.substr(0,2));
 if(trimmed.substr(2,2)!=="")
 numbers.push(trimmed.substr(2,2));
 if(trimmed.substr(4,4)!="")
 numbers.push(trimmed.substr(4,4));
input.value = numbers.join('-');

  }
}

1. First issue was you were trimming with length 8 , it should be 10 (including '-')

   2. Then for loop your were always increment 2 , that will not work out as we require 4 values in last item.

   3. Also you need to remove '-' before further you proceed with your logic.

check this

https://stackblitz.com/edit/angular-8dnjfw