How to get a list of associative array keys in JavaScript ?
Associative Array: Associative arrays are used to store key-value pairs. For example, to store the marks of the different subjects of a student in an array, a numerically indexed array would not be the best choice. Instead, we could use the respective subjects’ names as the keys in our associative array, and the value would be their respective marks gained. In an associative array, the key-value pairs are associated with a symbol.
Methods to get list of Associative Array Keys:
- using JavaScript foreach loop
- using Object.keys() method
- using Object.getOwnPropertyNames() method
Method 1: Using JavaScript foreach loop
In this method, traverse the entire associative array using a foreach loop and display the key elements of the array.
Syntax:
for (let key in dictionary) {
// do something with key
}
Example: In this example, we will loop through the associative array and print keys of the array.
javascript
// Script to Print the keys using loop// Associative arraylet arr = { Newton: "Gravity", Albert: "Energy", Edison: "Bulb", Tesla: "AC",};console.log("Keys are listed below");// Loop to print keysfor (let key in arr) { if (arr.hasOwnProperty(key)) { // Printing Keys console.log(key); }} |
Keys are listed below Newton Albert Edison Tesla
Method 2: Using Object.keys() method
The Object.keys() is an inbuilt function in javascript that can be used to get all the keys of the array.
Syntax:
Object.keys(obj)
Example: Below program illustrates the use of Object.keys() to access the keys of the associative array.
javascript
// Script to Print the keys// using Object.keys() function// Associative arraylet arr = { Newton: "Gravity", Albert: "Energy", Edison: "Bulb", Tesla: "AC",};// Get the keyslet keys = Object.keys(arr);console.log("Keys are listed below ");// Printing keysconsole.log(keys); |
Keys are listed below [ 'Newton', 'Albert', 'Edison', 'Tesla' ]
Method 3: Using Object.getOwnPropertyNames() method
The Object.getOwnPropertyNames() method in JavaScript is a standard built-in object which returns all properties that are present in a given object except for those symbol-based non-enumerable properties.
Syntax:
Object.getOwnPropertyNames(obj)
Example: In this example, we will use JavaScript Object.getOwnPropertyNames() method to get all the keys of the Given Associative array.
Javascript
// Input Associative Arraylet arr = { Newton: "Gravity", Albert: "Energy", Edison: "Bulb", Tesla: "AC",};// getting keys using getOwnPropertyNamesconst keys = Object.getOwnPropertyNames(arr);console.log("Keys are listed below ");// Display outputconsole.log(keys); |
Keys are listed below [ 'Newton', 'Albert', 'Edison', 'Tesla' ]
