Default Parameters in ES6 - in classes

es6-default-parameter-in-class-example.js

/**
A simple example of default parameter handling inside a JavaScript class which uses a constructor
*/
class paramValueExample {
  constructor(x, y) {
    this.x = 25;
    this.y = 50;
    
    this.fruits = ['banana', 'apple', 'grapes'];
    
    this.persons = {
      person: {
        name: 'Bob Martyn',
        age: 47,
        location: 'Australia'
      }
    };
  }

  handleDefaultParamters = (xp = 10, yp = 20, objPersons = {}) => {
    console.log(xp, yp);
    
    this.x = xp;
    this.y = yp;
    
    console.log(this.persons);
    
    this.persons = objPersons;
    console.log(`${xp + yp}`, this.fruits, this.persons);
  }
}

const newPersons = {
  person: {
    name: 'Jacob Schwartz',
    age: 38,
    location: 'USA'
  }
}

/**
Instantiate the class and create an objet of it
*/
const pve = new paramValueExample();

/**
Call the function and send some values and skip an intermediate parameter.
The keyword 'undefined' forces ES6 to use the default value set for that parameter.
*/
pve.handleDefaultParamters(35, undefined, newPersons);

// More explanations could be found at
https://gist.github.com/emfluenceindia/cbb89527c47f148bdff74cd50e60c5a8