How to make an object constructor that takes functions in Javascript?

Question

I'm trying to pass this simple test for an assignment and I'm having trouble figuring out how to right the constructor function for it,

describe("Student", function(){
  var student;

  beforeEach(function(){
    student = new Student({firstName: "Lysette", scores: [100, 100, 100, 4, 100]});
  });

  describe("name", function() {
    it("has a first name", function() {
      expect(student.firstName).toEqual("Lysette");
    });
  });

I've tried this, but it doesn't seem to be working:

var Student = function (firstName, scores){
  this.firstName = firstName;
  this.scores = scores;
};

Any Solutions?

You are passing an object containing two properties, `firstName` and `scores`, and not two separate parameters. Which of those behaviors do you want? — Scott Sauyet, May 24 '17 at 15:24
What does this have to do with the constructor taking functions? — Bergi, May 24 '17 at 16:04

Jonas Wilms · Answer 1 · 2017-05-24T15:37:04.027

0

You may use parameter destructuring (ES6):

var Student = function ({firstName, scores}){
  this.firstName = firstName;
  this.scores = scores;
};

Using this,you can just assign firstName and Scores.

Or old, but bulletproof, and assigning all propertys:

var Student = function (changes){
Object.assign( this,changes);
};

So you can do:

new Student({test:true,name:"test"});

Or if you want your original code, you may call it differently:

new Student("Jeff",[0,1,1]);

As youre expecting two parameters in your function...

edited May 24 '17 at 15:37

answered May 24 '17 at 15:24

Jonas Wilms

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@CarlosG90 actually i think the secons one is the best for you. Please read https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Operators/Destrukturierende_Zuweisung before using the first one... – Jonas Wilms May 24 '17 at 15:27

Glen Pierce · Answer 2 · 2017-05-24T15:40:26.830

0

Since functions are first class objects in JavaScript (What is meant by 'first class object'?), they can be passed like objects. This would be similar to how you might use a callback.

function Student(name, functionToBeCalledWhenCreated) // Constructor{
    this.name = name;
    functionToBeCalledWhenCreated(name);
}
function sayStudentsName(name){
    console.log("This student's name is " + name);
}

var glen = new Student("Glen", console.log); //don't include parenthesis on the function or it will call the function
var owen = new Student("Owen", sayStudentsName);

edited May 24 '17 at 15:40

answered May 24 '17 at 15:26

Glen Pierce

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you need to use `new` keyword: var glen = new Student("Glen", console.log) – angular_learner May 24 '17 at 15:31
Thanks for the remainder. – Glen Pierce May 24 '17 at 15:32

score 0 · Answer 3 · answered May 24 '17 at 15:28

0

You can construct student like this:

function Student(fields){
   this.firstName = fields.firstName;
   .......
}

answered May 24 '17 at 15:28

Alex Lyalka

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score 0 · Answer 4 · answered May 24 '17 at 16:03

0

Maybe you can try something like this :

class Student
{
  constructor(firstName, scores) 
  {
    this.firstName = firstName;
    this.scores = scores;
  }
}
var student = new Student('Lysette', [100, 100, 100, 4, 100]);
alert('Name : '+student.firstName+ ' | Scores : '+ student.scores);

answered May 24 '17 at 16:03

Mr972

26
2

This is just syntactic sugar for what the OP is doing already. – 4castle May 24 '17 at 16:39

How to make an object constructor that takes functions in Javascript?

4 Answers4