JavaScript class styles (from https://gist.github.com/tcrosen)

basic_class.js

class Person {
  constructor(props) {
    this.firstName = props.firstName || 'John';
    this.lastName = props.lastName || 'Doe';
  }

  getFullName() {
    return this.firstName + ' ' + this.lastName;
  }
}

console.log(new Person().getFullName());  // John Doe

basic_destructured.js

class Person {
  constructor({ firstName, lastName }) {
    this.firstName = firstName || 'John';
    this.lastName = lastName || 'Doe';
  }

  getFullName() {
    return this.firstName + ' ' + this.lastName;
  }
}

console.log(new Person({}).getFullName());
console.log(new Person({ lastName: 'Smith' }).getFullName());  // John Smith


/*
 * -----------------------------------
 * ALTERNATIVE WITH DEFAULT PARAMETERS
 * -----------------------------------
 */
class Person {
  constructor({ firstName = 'John', lastName = 'Doe' }) {
    this.firstName = firstName;
    this.lastName = lastName;
  }

  getFullName() {
    return this.firstName + ' ' + this.lastName;
  }
}

console.log(new Person({}).getFullName());         // John Doe
console.log(new Person({ lastName: 'Smith' }).getFullName());  // John Smith

constructor_alternative.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);
}

the_old_way.js

function Person(props) {
  this.firstName = props.firstName;
  this.lastName = props.lastName;
}

Person.prototype.getFullName = function() {
  return this.firstName + ' ' + this.lastName;
}