Properties in Methods

Let's dive deeper into the usage of object methods and explore how methods use the this keyword to access object properties.

Access Object Properties in Methods

When we define a method within an object, we can access the object's properties using the this keyword. this refers to the object called the method, allowing us to interact with its properties. Let's illustrate this concept with an example:

In the getInfo method, this refers to the furniture object and represents the entire object's inner content.

Practical Example

In methods, we can access object properties through this and then use dot notation to access the specific properties as usual.

In the example below, the methods getColor, addProperty, and modifyProperty use this to access the furniture property and perform various operations.

getColor logs the wardrobe color to the console using this to refer to the object's properties;
addProperty adds new properties to the furniture object. It takes two parameters: propertyName (the name of the new property) and propertyValue (the value to assign to the new property);
modifyProperty changes the value of an existing property in the furniture object. It takes two parameters: propertyName (the property name to modify) and propertyValue (the new value to assign to the property).


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const furniture = {
  type: "wardrobe",
  manufacturer: "Belgium",
  color: "wenge magic",

  getColor() {
    console.log(this.color);
  },

  addProperty(propertyName, propertyValue) {
    this[propertyName] = propertyValue;
  },

  modifyProperty(propertyName, propertyValue) {
    this[propertyName] = propertyValue;
  },
};

// Access the `color` property of the `furniture` and log it to the console.
furniture.getColor(); // Output: wenge magic

// Add a new property to the `furniture` object using the `addProperty` method.
furniture.addProperty("material", "wood");
console.log(furniture.material); // Output: wood

// Modify an existing property using the `modifyProperty` method.
furniture.modifyProperty("color", "oak");
console.log(furniture.color); // Output: oak

Note

Using the this keyword is essential in object methods. It ensures that the method works with the specific object that is called it, even if the name is unknown in advance. This avoids potential issues, such as copying methods from one object to another with a different name.

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Section 2. Chapter 10