How to call a Ts function in angular without Ngif or click function?

My Answer is different from other implementations because I would suggest you to use a pipe instead of calling the method in your template :

<td>
{{ employee | employeePipe }}
</td>

And this how your epmloyee-pipe.ts looks :

import { Pipe, PipeTransform } from '@angular/core';

@Pipe({
  name: 'employeePipe'
})
export class employeePipe implements PipeTransform {

  transform(employee: EmployeeModel): string {
    switch (employee.result) {
      case 'Excellent' : return 'Fonctionnel';
      case  'Good': return 'Technique';
      default:
              return 'Reject'
        break;
    }
    return null;
  }

}