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JavaScript . , ('') . . . , , , .
JavaScript , () . JavaScript .
JavaScript (entity). , , , , . JavaScript .
JavaScript . . JavaScript , . .
objectName.propertyName;
JavaScript , ( ) . . myCar , make, model, year .
const myCar = new Object();
myCar.make = "Ford";
myCar.model = "Mustang";
myCar.year = 1969;
const myCar = {
make: "Ford",
model: "Mustang",
year: 1969,
};
myCar.color; // undefined
JavaScript ( ) . ' '(associative array) , . myCar .
myCar["make"] = "Ford";
myCar["model"] = "Mustang";
myCar["year"] = 1969;
JavaScript , . JavaScript ( , ) . , . .
//
//
const myObj = new Object(),
str = "myString",
rand = Math.random(),
obj = new Object();
myObj.type = " ";
myObj["date created"] = " ";
myObj[str] = " ";
myObj[rand] = " ";
myObj[obj] = "";
myObj[""] = " ";
console.log(myObj);
. JavaScript () ( , [] ). , myObj obj JavaScript obj.toString() .
.
let propertyName = "make";
myCar[propertyName] = "Ford";
propertyName = "model";
myCar[propertyName] = "Mustang";
for...in . , .
function showProps(obj, objName) {
let result = "";
for (let i in obj) {
// obj.hasOwnProperty()
if (obj.hasOwnProperty(i)) {
result += `${objName}.${i} = ${obj[i]}\n`;
}
}
console.log(result);
}
showProps(myCar, 'myCar') .
myCar.make = Ford myCar.model = Mustang myCar.year = 1969
.
Object.keys(o). o ( ) ("") .Object.getOwnPropertyNames(o). o ( ) ("") .'' ( , ) . .
function listAllProperties(o) {
let objectToInspect = o;
let result = [];
while (objectToInspect !== null) {
result = result.concat(Object.getOwnPropertyNames(objectToInspect));
objectToInspect = Object.getPrototypeOf(objectToInspect);
}
return result;
}
" " . " "(Object initializer) C++ .
.
const obj = {
property_1: value_1, //
2: value_2, //
// ...,
"property n": value_n, //
};
obj , (, , ), value_i . obj , . ( )
. . new Object() . Object .
cond x .
let x;
if (cond) {
x = { greeting: "" };
}
myHonda . engine .
const myHonda = {
color: "red",
wheels: 4,
engine: { cylinders: 4, size: 2.2 },
};
, .
new . , , . . Car , , .
function Car(make, model, year) {
this.make = make;
this.model = model;
this.year = year;
}
this .
mycar .
var mycar = new Car("Eagle", "Talon TSi", 1993);
mycar . mycar.make "Eagle", mycar.year 1993 .
new Car .
const kenscar = new Car("Nissan", "300ZX", 1992);
const vpgscar = new Car("Mazda", "Miata", 1990);
. Person .
function Person(name, age, sex) {
this.name = name;
this.age = age;
this.sex = sex;
}
Person .
const rand = new Person("Rand McKinnon", 33, "M");
const ken = new Person("Ken Jones", 39, "M");
Car , Person owner .
function Car(make, model, year, owner) {
this.make = make;
this.model = model;
this.year = year;
this.owner = owner;
}
, .
const car1 = new Car("Eagle", "Talon TSi", 1993, rand);
const car2 = new Car("Nissan", "300ZX", 1992, ken);
rand ken . car2 .
car2.owner.name;
. ,
car1.color = "black";
car1 color 'black' . . Car .
Object.create Object.create() . .
//
const Animal = {
type: "", //
displayType: function () {
//
console.log(this.type);
},
};
// animal1
const animal1 = Object.create(Animal);
animal1.displayType(); // :
// fish
const fish = Object.create(Animal);
fish.type = "";
fish.displayType(); // :
. , .
( Car ) , (myCar.color = 'red') . myCar[5] = '25 mpg' myCar[5] .
HTML , document.forms , ( ) . <form> name="myForm" document.forms[1], document.forms['myForm'], document.forms.myForm .
prototype . . Car color , car1 .
Car.prototype.color = null;
car1.color = "black";
objectName.methodName = functionName;
const myObj = {
myMethod: function(params) {
// ...
}
//
myOtherMethod(params) {
// ...
}
};
objectName , methodName , functionname .
.
object.methodName(params);
. Car .
function displayCar() {
const result = ` ${this.year} ${this.make} ${this.model}`;
prettyPrint(result);
}
prettyPrint . this .
Car .
this.displayCar = displayCar;
Car .
function Car(make, model, year, owner) {
this.make = make;
this.model = model;
this.year = year;
this.owner = owner;
this.displayCar = displayCar;
}
displayCar .
car1.displayCar();
car2.displayCar();
this JavaScript this . this . Managerand Intern . name, age, job . sayHi() this.name . ', ', name, '.' .
const Manager = {
name: "John",
age: 27,
job: " ",
};
const Intern = {
name: "Ben",
age: 21,
job: " ",
};
function sayHi() {
console.log(`, ${this.name}.`);
}
// sayHi
Manager.sayHi = sayHi;
Intern.sayHi = sayHi;
Manager.sayHi(); // , John .'
Intern.sayHi(); // , Ben .'
this . howOldAmI() .
function howOldAmI() {
console.log(` ${this.age}.`);
}
Manager.howOldAmI = howOldAmI;
Manager.howOldAmI(); // 27.
...
const o = {
a: 7,
get b() {
return this.a + 1;
},
set c(x) {
this.a = x / 2;
},
};
console.log(o.a); // 7
console.log(o.b); // 8 <-- get b()
o.c = 50; // <-- set c(x)
console.log(o.a); // 25
o .
o.a o.b o.a 1 o.c o.c o.a "[gs]et property()" . [gs]et propertyName(){ } .
Object.defineProperties() . , / , / . / .
const o = { a: 0 };
Object.defineProperties(o, {
b: {
get: function () {
return this.a + 1;
},
},
c: {
set: function (x) {
this.a = x / 2;
},
},
});
o.c = 10; // , a 10 / 2 = 5
console.log(o.b); // , a + 1 = 6
. . . JavaScript , .
delete .
// a b
const myobj = new Object();
myobj.a = 5;
myobj.b = 12;
// a b
delete myobj.a;
console.log("a" in myobj); // : false
JavaScript . , .
// ,
const fruit = { name: "" };
const fruitbear = { name: "" };
fruit == fruitbear; // false
fruit === fruitbear; // false
// ,
const fruit = { name: "" };
const fruitbear = fruit; // fruit fruitbear
// fruit fruitbear
fruit == fruitbear; // true
fruit === fruitbear; // true
fruit.name = "";
console.log(fruitbear); // : { name: "" } { name: "" }
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