You want to map values of an array to function parameters in ES5.
\napply() methodGiven: a function that takes different parameters and an array containing concrete arguments.
\nfunction add(x, y, z) {\n return x + y + z;\n}\nvar parameters = [2, 3, 4];Naive solution, but also very verbose: access array values by index.
\nvar result = add(\n parameters[0],\n parameters[1],\n parameters[2]\n);\nconsole.log(result); // 9Better to use the apply() method (at least when you are in ES5).
...\nvar parameters = [2, 3, 4];\nvar result = add.apply(null, parameters);\nconsole.log(result); // 9Since ES2015: use the spread operator, which can be used to map array values to function parameters:
\n...\nlet parameters = [2, 3, 4];\nlet result = add(...parameters);\nconsole.log(result); // 9You want to define a static property inside a “class”.
\nCreate a “class”.
\nclass SomeClass {\n constructor(property) {\n this.property = property;\n }\n}Add the property that should be static directly to the “class”.
\nclass SomeClass {\n constructor(property) {\n this.property = property;\n }\n}\nSomeClass.STATIC_PROPERTY = 'This is a static property.';Voilá, there you got your static property.
\nconsole.log(SomeClass.STATIC_PROPERTY); // \"This is a static property.\"Static properties cannot be accessed via an instance:
\nlet instance = new SomeClass();\n// console.log(instance.STATIC_PROPERTY); // won't workTo access a static property based on an instance you need to access it via the constructor property:
let instance = new SomeClass();\nconsole.log(instance.constructor.STATIC_PROPERTY);You want to define a static method inside a “class”.
\nstatic keywordCreate a “class”.
\nclass SomeClass {\n constructor(property) {\n this.property = property;\n }\n}Add a method to that class (at this moment it is not static).
\nclass SomeClass {\n constructor(property) {\n this.property = property;\n }\n someStaticMethod() {\n console.log('someStaticMethod');\n }\n}Add the static keyword before the method name to make it static.
class SomeClass {\n constructor(property) {\n this.property = property;\n }\n static someStaticMethod() {\n console.log('This is a static method');\n }\n}Voilá, there you got a static method.
\nSomeClass.someStaticMethod(); // \"This is a static method\"Static methods cannot be called on an instance:
\nlet instance = new SomeClass();\n// instance.someStaticMethod(); // won't workTo call a static method based on an instance you need to call it via the constructor property:
let instance = new SomeClass();\ninstance.constructor.someStaticMethod();You want to apply inheritance using the class syntax introduced in ES2015.
\nextends keywordsuper keywordDefine a “class”. Optionally define some properties, getter and setters.
\n'use strict';\nclass Animal {\n constructor(color) {\n this._color = color;\n }\n get color() {\n return this._color;\n }\n set color(color) {\n this._color = color;\n }\n}Define some methods in that “class”.
\n'use strict';\nclass Animal {\n constructor(color) {\n this._color = color;\n }\n ...\n makeSound() {\n console.log('Generic animal cannot make any sound.');\n }\n}Define another “class” as “subclass” using the extends keyword. Optionally defined some properties, getters and setters.
...\nclass Dog extends Animal {\n constructor(name, color) {\n this._name = name;\n }\n get name() {\n return this._name;\n }\n set name(name) {\n this._name = name;\n }\n}Call the super constructor using super(), passing the parameters expected by the super constructor.
...\nclass Dog extends Animal {\n constructor(name, color) {\n super(color);\n this._name = name;\n }\n get name() {\n return this._name;\n }\n set name(name) {\n this._name = name;\n }\n}Optional: overwrite some methods in the “subclass”.
\n...\nclass Dog extends Animal {\n ...\n makeSound() {\n console.log('Wuff wuff');\n }\n}Voilá, there you got a perfect, tasteful ES2015 inheritance.
\n'use strict';\nclass Animal {\n constructor(color) {\n this._color = color;\n }\n get color() {\n return this._color;\n }\n set color(color) {\n this._color = color;\n }\n makeSound() {\n console.log('Generic animal cannot make any sound.');\n }\n}\nclass Dog extends Animal {\n constructor(name, color) {\n super(color);\n this._name = name;\n }\n get name() {\n return this._name;\n }\n set name(name) {\n this._name = name;\n }\n makeSound() {\n console.log('Wuff wuff');\n }\n}\nlet dog = new Dog('Bello', 'brown');\nconsole.log(dog.name); // \"Bello\"\nconsole.log(dog.color); // \"brown\"\nconsole.log(dog instanceof Dog); // true\nconsole.log(dog instanceof Animal); // true\ndog.makeSound(); // \"Wuff wuff\"\nlet animal = new Animal('yellow');\nconsole.log(animal.color); // \"yellow\"\nconsole.log(animal instanceof Animal); // true\nconsole.log(animal instanceof Dog); // false\nanimal.makeSound(); // \"Generic animal cannot make any sound.\"You want to create getters and setters for a class in ES2015.
\nget and set keywordsCreate a class with some properties.
\nclass Person {\n constructor(firstName, lastName) {\n this._firstName = firstName;\n this._lastName = lastName;\n }\n}Add methods that return the properties.
\nclass Person {\n constructor(firstName, lastName) {\n this._firstName = firstName;\n this._lastName = lastName;\n }\n firstName() {\n return this._firstName;\n }\n lastName() {\n return this._lastName;\n }\n}Define those methods as getters using the get keyword.
class Person {\n constructor(firstName, lastName) {\n this._firstName = firstName;\n this._lastName = lastName;\n }\n get firstName() {\n return this._firstName;\n }\n get lastName() {\n return this._lastName;\n }\n}Add methods that sets new values to the properties.
\nclass Person {\n constructor(firstName, lastName) {\n this._firstName = firstName;\n this._lastName = lastName;\n }\n firstName(value) {\n this._firstName = value;\n }\n get firstName() {\n return this._firstName;\n }\n lastName(value) {\n this._lastName = value;\n }\n get lastName() {\n return this._lastName;\n }\n}Define those methods as setters using the set keyword.
class Person {\n constructor(firstName, lastName) {\n this._firstName = firstName;\n this._lastName = lastName;\n }\n set firstName(value) {\n this._firstName = value;\n }\n get firstName() {\n return this._firstName;\n }\n set lastName(value) {\n this._lastName = value;\n }\n get lastName() {\n return this._lastName;\n }\n}Voilá, there you got perfect getters and setters.
\nlet person = new Person('John', 'Doe');\nconsole.log(person.firstName); // \"John\"\nconsole.log(person.lastName); // \"Doe\"\nperson.firstName = 'Jane'; // \"Jane\"\nconsole.log(person.lastName); // \"Doe\"_firstName and _lastName) and for the accessor properties (e.g., firstName and lastName).\nOtherwise you will have an endless loop.Getters and setters does not prevent you from accessing the underlying properties directly:
\nlet person = new Person('John', 'Doe');\nconsole.log(person._firstName); // \"John\"\nconsole.log(person._lastName); // \"Doe\"\nperson._firstName = 'Jane'; // \"Jane\"\nconsole.log(person.firstName); // \"Jane\"Validation of property values
\nclass Person {\n ...\n set firstName(value) {\n if(typeof value !== 'string') {\n throw new TypeError('First name must be of type string.');\n }\n this._firstName = value;\n }\n ...\n}getFirstName(), setFirstName())