JavaScript: List the properties of a JavaScript object

Last update on May 30 2022 09:59:04 (UTC/GMT +8 hours)

JavaScript Object: Exercise-1 with Solution

Write a JavaScript program to list the properties of a JavaScript object.
Sample object:
var student = {
name : "David Rayy",
sclass : "VI",
rollno : 12 };
Sample Output: name,sclass,rollno

Sample Solution: -

HTML Code:

<!DOCTYPE html>
  <html>
  <head>
  <meta charset="utf-8">
  <title>JavaScript program to list the properties of a JavaScript object. </title>
  </head>
  <body>
</body>
  </html>

JavaScript Code:

function _keys(obj) 
 {
    if (!isObject(obj)) return [];
    if (Object.keys) return Object.keys(obj);
    var keys = [];
    for (var key in obj) if (_.has(obj, key)) keys.push(key);
    return keys;
  }
function isObject(obj) 
{
    var type = typeof obj;
    return type === 'function' || type === 'object' && !!obj;
  }
console.log(_keys({red: "#FF0000", green: "#00FF00", white: "#FFFFFF"}));

Sample Output:

["red","green","white"]

Flowchart:

Live Demo:

See the Pen javascript-object-exercise-1 by w3resource (@w3resource) on CodePen.

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Previous: javascript Object Eexercises.
Next: Write a JavaScript program to delete the rollno property from the following object. Also print the object before or after deleting the property.

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JavaScript: Tips of the Day

How to insert an item into an array at a specific index (JavaScript)?

What you want is the splice function on the native array object.

arr.splice(index, 0, item); will insert item into arr at the specified index (deleting 0 items first, that is, it's just an insert). In this example we will create an array and add an element to it into index 2:

var arr = [];
arr[0] = "Jani";
arr[1] = "Hege";
arr[2] = "Stale";
arr[3] = "Kai Jim";
arr[4] = "Borge";

console.log(arr.join());
arr.splice(2, 0, "Lene");
console.log(arr.join());

Ref: https://bit.ly/2BXbp04