You want to use pseudoclassical inheritance, i.e., create a “class” as “subclass” of another “class”.
\nprototype propertycall() methodDefine a function intended to be a constructor function (this will be the “superclass”).
\nfunction Animal(color) {\n this._color = color;\n}Define some properties and/or methods on the prototype of that function. Those are the members of the “class”.
\nfunction Animal(color) {\n this._color = color;\n}\nAnimal.prototype.getColor = function() {\n return this._color;\n}\nAnimal.prototype.makeSound = function() {\n console.log('Generic animal cannot make any sound.');\n}Define another function intended to be a constructor function based on the previously defined function (this will be the “subclass”).
\n...\nfunction Dog(name, color) {\n this._name = name;\n}Set the prototype property of that function.
...\nfunction Dog(name, color) {\n this._name = name;\n}\nDog.prototype = new Animal();Call the super constructor function using the call() method, passing this and the parameters expected by the super constructor.
...\nfunction Dog(name, color) {\n Animal.call(this, color);\n this._name = name;\n}\nDog.prototype = new Animal();Define some properties and/or methods on the prototype of that function.
\n...\nfunction Dog(name, color) {\n Animal.call(this, color);\n this._name = name;\n}\nDog.prototype = new Animal();\nDog.prototype.getName = function() {\n return this._name;\n}Optional: overwrite methods by defining them on the prototype of the “subclass”.
\n...\nfunction Dog(name, color) {\n Animal.call(this, color);\n this._name = name;\n}\nDog.prototype = new Animal();\nDog.prototype.getName = function() {\n return this._name;\n}\nDog.prototype.makeSound = function() {\n console.log('Wuff wuff');\n}Voilá, there you got a perfect pseudoclassical inheritance.
\nfunction Animal(color) {
\n this._color = color;
\n}\n
Animal.prototype.getColor = function() {
\n return this._color;\n}
\nAnimal.prototype.makeSound = function() {
\n console.log('Generic animal cannot make any sound');\n
}\nfunction Dog(name, color) {\n Animal.call(this, color);\n this._name = name;\n}\nDog.prototype = new Animal();\nDog.prototype.getName = function() {\n return this._name;\n}\nDog.prototype.makeSound = function() {\n console.log('Wuff wuff');\n}\n\nvar dog = new Dog('Bello', 'brown');\nconsole.log(dog.getName()); // \"Bello\"\nconsole.log(dog.getColor()); // \"brown\"\nconsole.log(dog instanceof Dog); // true\nconsole.log(dog instanceof Animal); // true\ndog.makeSound(); // \"Wuff wuff\"\nvar animal = new Animal('yellow');\nconsole.log(animal.getColor()); // \"yellow\"\nconsole.log(animal instanceof Animal); // true\nconsole.log(animal instanceof Dog); // false\nanimal.makeSound(); // \"Generic animal cannot make any sound.\"Since ES2015: use class syntax, which is syntactic sugar for pseudoclassical inheritance.
\nclass Animal {\n ...\n}\nclass Dog extends Animal {\n ...\n}You want to convert the array-like object arguments to a real array.
Array prototypeslice() methodcall() methodGiven: a function that takes different parameters and accesses them via the arguments object.
function printAllArguments() {\n let values = arguments;\n for(let i=0; i<values.length; i++) {\n console.log(values[i]);\n }\n}\nprintAllArguments(2, 3, 4);Get a reference to the Array prototype.
function printAllArguments() {\n let arrayPrototype = Array.prototype;\n ...\n}\n...Get a reference to the slice() method. (The slice() method creates a shallow copy of a part of an array and returns a new array. If you omit any parameters it copies the whole array.)
function printAllArguments() {\n let arrayPrototype = Array.prototype;\n let sliceMethod = arrayPrototype.slice;\n ...\n}\n...Call the slice() method using the call() method.
function printAllArguments() {\n let arrayPrototype = Array.prototype;\n let sliceMethod = arrayPrototype.slice;\n let values = sliceMethod.call(arguments);\n for(let i=0; i<values.length; i++) {\n console.log(values[i]);\n }\n}\nprintAllArguments(2, 3, 4);Combine the code from the previous three steps.
\nfunction printAllArguments() {\n let values = Array.prototype.slice.call(arguments);\n for(let i=0; i<values.length; i++) {\n console.log(values[i]);\n }\n}\nprintAllArguments(2, 3, 4);Voilá, there you got a real array now, e.g., you can call array methods like forEach, map, reduce and filter on it.
function printAllArguments() {\n let values = Array.prototype.slice.call(arguments);\n values.forEach(function(value) {\n console.log(value);\n });\n}\nprintAllArguments(2, 3, 4);Since ES2015: use Array.from() to create an array based on an array-like object:
function printAllArguments() {\n let values = Array.from(arguments);\n values.forEach(function(value) {\n console.log(value);\n });\n}\nprintAllArguments(2, 3, 4);And while you are in ES2015 you can also use fat arrow functions:
\nfunction printAllArguments() {\n let values = Array.from(arguments);\n values.forEach((value) => {\n console.log(value);\n });\n}\nprintAllArguments(2, 3, 4);And while you are at it, use rest parameters, which are real arrays:
\nfunction printAllArguments(...values) {\n values.forEach((value) => {\n console.log(value);\n });\n}\nprintAllArguments(2, 3, 4);You want to emulate block level scope in ES5 to prevent naming conflicts.
\nGiven: some code that you want to put in a block.
\nvar aVariable = 2345;\n// Block should start here\nvar aVariable = 4711;\nconsole.log(aVariable); // should print 4711\n// Block should end here\nconsole.log(aVariable); // should print 2345, but prints 411Put the code into an anonymous function.
\nvar aVariable = 2345;\nfunction() {\n var aVariable = 4711;\n console.log(aVariable);\n}\nconsole.log(aVariable);Put the function into a pair of rounded brackets.
\nvar aVariable = 2345;\n(function() {\n var aVariable = 4711;\n console.log(aVariable);\n});\nconsole.log(aVariable);Append another pair of rounded brackets. This actually calls the defined function.
\nvar aVariable = 2345;\n(function () {\n var aVariable = 4711; // prints 4711\n console.log(aVariable);\n})();\nconsole.log(aVariable); // prints 2345Variant 1: put brackets at the end (as shown in the recipe)
\n(function() {\n var aVariable = 4711;\n console.log(aVariable);\n})();Variant 2: put brackets inside
\n(function() {\n var aVariable = 4711;\n console.log(aVariable);\n}());let keyword, which provides a native way of declaring block scoped variables.