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JavaScript Object - Exercises, Practice, Solution

JavaScript Object [18 exercises with solution]

[An editor is available at the bottom of the page to write and execute the scripts.]

1. Write a JavaScript program to list the properties of a JavaScript object. Go to the editor
Sample object:
var student = {
name : "David Rayy",
sclass : "VI",
rollno : 12 };
Sample Output: name,sclass,rollno
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2. Write a JavaScript program to delete the rollno property from the following object. Also print the object before or after deleting the property. Go to the editor
Sample object:
var student = {
name : "David Rayy",
sclass : "VI",
rollno : 12 };
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3. Write a JavaScript program to get the length of a JavaScript object. Go to the editor
Sample object :
var student = {
name : "David Rayy",
sclass : "VI",
rollno : 12 };
Click me to see the solution

4. Write a JavaScript program to display the reading status (i.e. display book name, author name and reading status) of the following books. Go to the editor

var library = [ 
   {
       author: 'Bill Gates',
       title: 'The Road Ahead',
       readingStatus: true
   },
   {
       author: 'Steve Jobs',
       title: 'Walter Isaacson',
       readingStatus: true
   },
   {
       author: 'Suzanne Collins',
       title:  'Mockingjay: The Final Book of The Hunger Games', 
       readingStatus: false
   }];

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5. Write a JavaScript program to get the volume of a Cylinder with four decimal places using object classes. Go to the editor
Volume of a cylinder : V = πr2h
where r is the radius and h is the height of the cylinder.
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6. Write a Bubble Sort algorithm in JavaScript. Go to the editor
Note : Bubble sort is a simple sorting algorithm that works by repeatedly stepping through the list to be sorted,
Sample Data: [6,4,0, 3,-2,1]
Expected Output : [-2, 0, 1, 3, 4, 6]
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7. Write a JavaScript program which returns a subset of a string. Go to the editor
Sample Data: dog
Expected Output: ["d", "do", "dog", "o", "og", "g"]
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8. Write a JavaScript program to create a Clock. Go to the editor
Note: The output will come every second.
Expected Console Output :
"14:37:42"
"14:37:43"
"14:37:44"
"14:37:45"
"14:37:46"
"14:37:47"
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9. Write a JavaScript program to calculate the area and perimeter of a circle. Go to the editor
Note : Create two methods to calculate the area and perimeter. The radius of the circle will be supplied by the user.
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10. Write a JavaScript program to sort an array of JavaScript objects. Go to the editor
Sample Object :

var library = [ 
   {
       title:  'The Road Ahead',
       author: 'Bill Gates',
       libraryID: 1254
   },
   {
       title: 'Walter Isaacson',
       author: 'Steve Jobs',
       libraryID: 4264
   },
   {
       title: 'Mockingjay: The Final Book of The Hunger Games',
       author: 'Suzanne Collins',
       libraryID: 3245
   }];

Expected Output:

[[object Object] {
  author: "Walter Isaacson",
  libraryID: 4264,
  title: "Steve Jobs"
}, [object Object] {
  author: "Suzanne Collins",
  libraryID: 3245,
  title: "Mockingjay: The Final Book of The Hunger Games"
}, [object Object] {
  author: "The Road Ahead",
  libraryID: 1254,
  title: "Bill Gates"
}]

Click me to see the solution

11. Write a JavaScript function to print all the methods in an JavaScript object. Go to the editor
Test Data :
console.log(all_properties(Array));
["length", "name", "arguments", "caller", "prototype", "isArray", "observe", "unobserve"]
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12. Write a JavaScript function to parse an URL. Go to the editor
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13. Write a JavaScript function to retrieve all the names of object's own and inherited properties. Go to the editor
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14. Write a JavaScript function to retrieve all the values of an object's properties. Go to the editor
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15. Write a JavaScript function to convert an object into a list of `[key, value]` pairs. Go to the editor
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16. Write a JavaScript function to get a copy of the object where the keys have become the values and the values the keys. Go to the editor
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17. Write a JavaScript function to check whether an object contains given property. Go to the editor
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18. Write a JavaScript function to check whether a given value is a DOM element. Go to the editor
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More to Come !

* To run the code mouse over on Result panel and click on 'RERUN' button.*

Live Demo:

See the Pen javascript-common-editor by w3resource (@w3resource) on CodePen.


Do not submit any solution of the above exercises at here, if you want to contribute go to the appropriate exercise page.



JavaScript: Tips of the Day

Array of nested arrays

const person = {
  name: 'Owen',
  age: 23,
};

for (const [x, y] of Object.entries(person)) {
  console.log(x, y);
}

Object.entries(person) returns an array of nested arrays, containing the keys and objects:
[ [ 'name', 'Owen' ], [ 'age', 23 ] ] Using the for-of loop, we can iterate over each element in the array, the subarrays in this case. We can destructure the subarrays instantly in the for-of loop, using const [x, y]. x is equal to the first element in the subarray, y is equal to the second element in the subarray.
The first subarray is [ "name", "Owen" ], with x equal to "name", and y equal to "Owen", which get logged. The second subarray is [ "age", 23 ], with x equal to "age", and y equal to 23, which get logged.

Ref: https://bit.ly/3jFRBje