export class RepeatPasswordDirective implements Validator,OnChanges {
/ * *

• check method
• @ param c
• @ returns {{[p: string]: any}}

* /
validate (c: AbstractControl): {[p: string]: any} {

return verifyPassword(c,this.repeatPassword.control);

}

ngOnChanges (changes: SimpleChanges): void {

  this.repeatPassword=changes["repeatPassword"].currentValue;

}

/ *

• pass in the model of another input tag through the attribute
The
• name is the same as the selector, so there is no need to add additional attributes to pass in
when using it.

* /
@ Input () repeatPassword:NgModel;
constructor () {}

}

validate (c: AbstractControl): {[p:string]: any} {
}
like this function, the return value is {[p:string]: any}. What does it mean to put a key-value pair in square brackets?