Finding entry by property in custom object array

Question

I'm developing an app in Angular 2 using Typescript and have a problem. I am having a service which fetches array of Questions looking like this

    export class Question {

    constructor(public id: number,
                public question_text: string,
                public answers: string[],
                public user_answer: string = "none") // default to none, update on user input

    {}
}

private questions: Question[] = [
    new Question(0, 
  'How often did you eat a portion of vegetables??', 
  ['Answer A','Answer B', 'Answer C', 'Answer D', 'Answer E', 'Answer F']),
    new Question(1, 
  'How often did you eat a portion of fruit?', 
  ['Answer A','Answer B', 'Answer C', 'Answer D', 'Answer E', 'Answer F']),

Then I am having a button which allows user to edit the Question (all the data including the id). My updateQuestion looks like this:

updateQuestion(questionId: number, newQuestion: Question) {
   //Find question in array
   //Delete this entry
   //Add new question to array

}

I am really struggling with the very first task: find question in an array. I have tried some combinations with

this.questions.find(question => questionId == id) 

but id is undefined there and I am not sure how to get to it.

Problem basically revolves around finding right entry in the questions array where id = questionId

Any help will be much appreciated!!

Answer 1

The Problem was with Question model. I have changed my Question model to be:

export class Question {

public _id: number;
public _question_text: string;
public _answers: string[];
public _user_answer: string;

constructor(public id: number,
            public question_text: string,
            public answers: string[],
            public user_answer: string = "none") // default to none, update on user input

{
    this._id = id;
    this._question_text = question_text;
    this._answers = answers;
    this._user_answer = user_answer;
}
}

And then my service:

updateQuestion(questionId: number, newQuestion: Question) {
    const questionIndex = this.questions.findIndex(x => x._id == questionId);