07_JS_Objects

Software-Engineering

---

# What are Objects in JS?

Everything can be an object. An object has properties & properties have values. Object = key-value pair. An object is a mutable data structure = content can be modified after it gets created.

# Creating Objects

const person = {
    lastName : "Schmid",
    isMarried : false,
    age : 18,
    skills : [
        "C#",
        "JavaScript",
        "RESTful API"
    ],
    getFullDetails : function() {
        return `${this.lastName} ${this.age} ${this.isMarried}`
    }      
}

---

# Get Values from Object

console.log(person.age)
console.log(person.isMarried)
console.log(person.getFullDetails())
/* Output
18
false
Schmid 18 false
*/

---

# Setting new Keys in an Object

In this example we have to look at the person object, we created above

person.age = 69
person.isMarried = true
person.skills.push("Python")
console.log(person)
/* Output
{lastName: 'Schmid', isMarried: true, age: 69, skills: Array(4), getFullDetails: f}
*/

---

# Object Manipulation

# object.assign()

to copy an object without modifying the original object

const copyPerson = Object.assign({}, person)
// Output
{
    "lastName": "Schmid",
    "isMarried": false,
    "age": 18,
    "skills": [
        "C#",
        "JavaScript",
        "RESTful API"
    ]
}

# object.keys()

to get the keys/properties of an object as array

const keys = Object.keys(copyPerson)
// Output
[
    "lastName",
    "isMarried",
    "age",
    "skills",
    "getFullDetails"
]

# object.values()

to get object values

const values = Object.values(copyPerson)
// Output
[
    "Schmid",
    false,
    18,
    [
        "C#",
        "JavaScript",
        "RESTful API"
    ],
    null
]

# object.entries

to get object keys & values

const entries = Object.entries(copyPerson)
// Output
// (5) [Array(2), Array(2), Array(2), Array(2), Array(2)]
[
    [
        "lastName",
        "Schmid"
    ],
    [
        "isMarried",
        false
    ],
    [
        "age",
        18
    ],
    [
        "skills",
        [
            "C#",
            "JavaScript",
            "RESTful API"
        ]
    ],
    [
        "getFullDetails",
        null
    ]
]

---

# Check properties using hasOwnProperty()

to check if a specific key/property exists in an object.

• bool

console.log(copyPerson.hasOwnProperty("skills"))
// Output
true