An object is a collection of properties , defined as a key-value pair. Each property has a key and a value. The property key can be a string and the property value can be any valid value.
Create an object
You can use {} or the new Object().
let object = {}
object.name = "Folau";
object.age = 33;
// or
let obj = new Object();
obj.name = "Folau";
obj.age = 33;
let user = {
"name": "Folau",
"age": 33
}
console.log("user: ", user);//{"name":"Folau","age":33}
Access field value with dot(.)
let user = {
"name": "Folau",
"age": 33
}
console.log("user name: ", user.name);//Folau
Access field value with []
let user = {
"name": "Folau",
"age": 33
}
console.log("user name: ", user['name']);//Folau
Remove or delete a key value with delete.
let user = {
"name": "Folau",
"age": 33
}
console.log("user: ", user);//{"name":"Folau","age":33}
/*
* To remove a property, we can use delete operator.
*/
delete user.age;
console.log("user: ", user);{"name":"Folau"}
let user = {
"name": "Folau",
"age": 33
}
console.log("user: ", user);//{"name":"Folau","age":33}
let doesUserHaveName = ("name" in user);
console.log("name in user: ", doesUserHaveName);//true
let doesUserHaveAddress = ("address" in user);
console.log("address in user: ", doesUserHaveAddress);//false
let user = {
"name": "Folau",
"age": 33
}
for(let field in user){
console.log("field: ", field, ", value: ", user[field]);
}
//Output
field: name , value: Folau
field: age , value: 33
Objects are mutable
let user = {
"name": "Folau",
"age": 33
}
let member = user;
member.name = "Lisa";
console.log("user: ", user);//{"name":"Lisa","age":33}
console.log("member: ", member);//{"name":"Lisa","age":33}
The object member is not a copy of user. It is user. Both member and user are the same object.
Any changes to member will also change user, because member and user are the same object.
Clone objects
Use object.assign(target, source…). By cloning an object, changes to that object do not reflect on the original object.
let person = {
name:"Folau",
age: 33,
score: {
sc: 100
}
}
console.log("person ", person);//{name: "Folau", age: 33, score: {sc: 100}}
person.score.sc = 25;
/*
* Clone objects
*/
let lau = Object.assign({}, person);
console.log("lau", lau);//{name: "Folau", age: 33, score: {sc: 25}}
Object.assign does not copy nested objects.
copyObject(obj){
let jsonString = JSON.stringify(obj);
return JSON.parse(jsonString);
}