OOP JavaScript notes

js_notes

// Reflection
typeof 100 => Number
object instanceof Object => true/false
Array.isArray(array_var) => true/false

// Detecting object properties
"property" in object => true/false               // checks own and prototype
object.hasOwnProperty("property") => true/false
Object.keys(object)                              // returns own properties only
for (var property in object) {}                  // loops over enumerable own and prototype properties

// this manipulation
function.call(this_object, args, ...);                       // executes function with new this
function.apply(this_object, [args, ...]);                    // executes function with new this
function.bind(this_object, permanent_overriding_args, ...);  // returns new function, permanently overwriting arg values

// Misc
delete object.property  // deletes own property from object

// Objects
var object = {
  this._prop,       // "private" data property
  get prop() {},    // accessor property
  set prop(arg) {}  // accessor property
}

Object.defineProperty(object, property, descriptor)
descriptor === {
  enumerable: t/f,            // data/accessor
  configurable: t/f,          // data/accessor; whether property can be changed
  writable: t/f,              // data only; whether property value can be changed
  value: "value of property", // data only
  get: function() {},         // accessor only
  set: function() {}          // accessor only
}
// All t/f default to true

Object.defineProperties(object, {
  prop_name: descriptor_object,
  prop2_name: descriptor_object,
  etc..
})

Object.create(prototype_object, {
  prop_name: descriptor_object,
  prop2_name: descriptor_object,
  etc..
})

Object.getOwnPropertyDescriptor(object, property) => retuns descriptor object
Object.preventExtensions(object) => prevents the addition of properties; Object.isExtensible(object)
Object.seal(object) => [[Extensible]] and [[Configurable]] are set to false; Object.isSealed(object)
Object.freeze(object) => sealed and property values can't be changed; Object.isFrozen(object)k

// Class
function Constructor() {
  this.data_properties,
  etc...
}

Constructor.prototype = {
  constructor: Constructor
  method: function() {},
  method2: function() {},
  etc...
}

// Inheritance
Constructor.prototype = prototype_object;  // ex: new OtherConstructor(); Object.create(OtherConstructor.prototype, {})
Constructor.prototype.constructor = Constructor;

// Constructor Stealing
function Constructor() {
  OtherConstructor.call(this, args...);
}
Constructor.prototype = new OtherConstructor();
Constructor.prototype.constructor = Constructor;