constructor-alternatives-1.js

// Destructuring alternative
constructor(props = {}) {
  const { firstName = 'John', lastName = 'Doe' } = props;
  
  this.firstName = firstName;
  this.lastName = lastName;
}

// Destructuring alternative
constructor(props) {
  const { firstName = 'John', lastName = 'Doe' } = props || {};
  
  this.firstName = firstName;
  this.lastName = lastName;
}

// Using Object.assign() (or _.assign)
constructor(props) {
  const defaults = {
    firstName: 'John', 
    lastName: 'Doe'
  };
  
  Object.assign(this, defaults, props);
}