JavaScript - Help me read and understand some of this code Please

Question

https://gyazo.com/d21d15807de53f20732a01537a06350d
If the text gets reformatted, then the link above is a screen shot of the code.
My questions:
1) the 'Person' was said to be a constructor. From what I understand, constructors instantiate an object--class / object literal with certain properties and behaviors. How is that a constructor because from what I know constructors are nested within a class. I'm not familiar with the syntax, can you point me to a resource on this ?
2) The for loop within the 'Person'. Can you point me to a resource explaining that syntax ' var key in data'.
3) For confirmation, the 'this' is referring to the instance of the Person object right ? I'm just bewildered by the syntax of the creation of the 'Person' and I don't know whether or not to treat it as an object or a class.
'use strict';
var Person = function (data) {
  for (var key in data) {
    this[key] = data[key];  
  }
  this.getKeys = function () {
    return Object.keys(this);
  }
}
var Alena = new Person({ name: 'Alena', role: 'Teacher' });
console.log('Alena\'s Keys:', Alena.getKeys()); // 'this' refers to 'Alena'
var getKeys = Alena.getKeys;
console.log(getKeys()); // 'this' refers to the node process

Steven Parker · Accepted Answer

1. The class syntax where you have a method named "constructor" nested inside a class is a recent addition to JavaScript.  The example shown here is the classic style where the constructor is created as a function that has the name of the class itself.  This should be explained in the class you are taking.
2. The loop is a "for...in" type.  Here's the MDN reference page for for...in (https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/for...in).
3. The keyword "this" used in a constructor is a reference to the new object instance being created.  There's a workshop here called Understanding "this" in JavaScript (https://teamtreehouse.com/library/understanding-this-in-javascript) you may enjoy.
And "Person" in this example is a class (and also the name of the constructor function for that class).  An example of an object would be "Alena".

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Victor Ibasco

Victor Ibasco

JavaScript - Help me read and understand some of this code Please

1 Answer

Steven Parker

Steven Parker