©2018  LUVCODING                             

HUDDERSFIELD

UK

luvcoding
  • Grey Facebook Icon
  • Grey Twitter Icon
  • Grey Google+ Icon
  • Grey YouTube Icon
  • Grey Pinterest Icon
luvcodings.com

working with Objects in Javascript

An object is a collection of properties, where properties are the  association between a name (or key) and a value. The value of a property can be a function, in which case the property is known as a method.

JavaScript object has properties associated with it. You can define your own objects, by creating,  properties, functions, and methods.

Converting objecjects to string

We can use the The JSON.stringify() method to converts JavaScript objects into strings.

Example:

<script>
    var color = {
        'red': [255, 0, 0],
       'blue': [0, 0, 255],
       'green': [0, 0, 255]
     }

   document.getElementById('demo').innerHTML=JSON.stringify(color);
 

Output:

// { "red": [ 255, 0, 0 ], "blue": [ 0, 0, 255 ], "green": [ 0, 0, 255 ] }

 

Get  the length/size of the object by the keys ( The keys are all the first element in the objects that comes before the colon (:))

  var dSize = Object.keys(color).length;
  document.getElementById('demo1').innerHTML=size;

Output:

// 3

Get  the length/size of the object by the keys ( The values are all the elements in the objects that comes after the colon (:))

  var dSize = Object.values(color).length;
  document.getElementById('demo').innerHTML=dSize;

Output:

// 3

</script>

Creating a new object

You can create a new object following the methods below():

Method 1: create an object by declaring the variables  once, separated by commas.

var myObj = new Object(),
    str , Subject, year; 

 

Then assign values to the keys.
    myObj.str             = 'hhgg';

    myObj[ 'Subject']     = 'Math';
    myObj['year']         ='2002'

  document.getElementById('demo').innerHTML=JSON.stringify(myObj);

Output:

{"str":"hhgg","Subject":"Math","year":"2002"}

Method 2: create an object by declaring  an empty object using the {} symbol 

var myObj ={};

Then populate the object with keys and values.
  myObj.id=77;
  myObj.name='object'
  myObj.style='standard'
  
  document.getElementById('demo').innerHTML=JSON.stringify(myObj);

Output:

{"id":77,"name":"object","style":"standard"}

Method 3: create an object and call it with a function from the object

var d_obj = {
    Country: 'Nigeria',
    Age:String(70) + 'years',
    History: function () {
        return this.Country + " " + this.Age;
    }
 }
  var details= d_obj.History();
  document.getElementById('demo').innerHTML=details;

Output:

Nigeria 70years

Method 4: create an object with existing value, using a constructor

function Car(age, sex, education) {   

    this.age = age;

    this.sex = sex;

    this.education = education;

}

Now Create new objects of the object

  var employee_1= new Employee(30, 'Male', 'PG');
  var employee_2= new Employee(22, 'Female', 'U_GRAD');

 

Get  object employee_2's age
  document.getElementById('demo').innerHTML= employee_2.age;

Now Create new property( instance variable) for employee_2

 employee_2.experience='Professional'
 document.getElementById('demo').innerHTML= employee_2.experience 

Related

Related