Can I assign a variable as value to an object's key?

Question

Is this allowed?

export class H{
passwordErrorMessage = 'Password must contain 1 small-case alphabet, 1 capital  alphabet, 1 digit, 1 special character. The length should be 6-10 characters.'
...

validatePassword(control: FormControl) {
...
    return (REG_EXP.test(password)) ? null : {
      validatePassword: { // check the class ShowErrorsComponent to see how validatePassword is used.
        valid: false,
        message:  this.passwordErrorMessage //can I do this?
      } 
    };
  }
}

For one of my test cases, I am getting the following error

TypeError: Cannot read property 'passwordErrorMessage' of undefined
Error object: Property name: ngDebugContext, value: [object Object]
Error object: Property name: ngErrorLogger, value: function () { [native code] }
TypeError: Cannot read property 'passwordErrorMessage' of undefined
    at HelperService.validatePassword (webpack:///./src/app/helper.service.ts?:224:31)

It seems this is undefined . I am still in early stages of debugging but my first doubt is if the usage of this is correct? Things work fine if I change the usage to message: 'Password must contain 1 small-case alphabet, 1 capital alphabet, 1 digit, 1 special character. The length should be 6-10 characters.' message: 'Password must contain 1 small-case alphabet, 1 capital alphabet, 1 digit, 1 special character. The length should be 6-10 characters.'

Answer 1

yes you can, but you'll need to either bind validatePassword to the class or use an arrow function to pass this context into the function. this should work:

export class H{
    passwordErrorMessage = 'Password must contain 1 small-case alphabet, 1 capital  alphabet, 1 digit, 1 special character. The length should be 6-10 characters.'
    ...

    validatePassword = (control: FormControl) => {
        ...
        return (REG_EXP.test(password)) ? null : {
          validatePassword: { // check the class ShowErrorsComponent to see how validatePassword is used.
            valid: false,
            message:  this.passwordErrorMessage
          } 
    };
  }
}