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How to add key/value pair to a JavaScript object ?
JavaScript object has key-value pair and it can be of variable length. We first need to declare an object and assign the values to that object for that there can be many methods. In this article, we are going to apply different approaches to adding a key/value pair to a JavaScript object.
These are the following methods to add a key/value pair to a JavaScript object:
Table of Content
- Using Dot Notation
- Using Bracket Notation
- Using Spread operator
- Using Objcet.assign() method
- Using Objcet.defineProperty() method
Method 1: Using Dot Notation
In this approach, we will directly access the key of an object by “.” for assigning the value to it. It can be a repeated method as every time we need to define a different key for different values.
Example: This example shows the implementation of the above approach.
Method 2: Using Bracket Notation
In this approach, we are using Bracket to access the key and assign the value to it.
Method 3: Using Spread operator
In this approach, we are using Spread operator to assign the value to the object. we will create a new object and by using the spread operator we can add the old key and value to the new object with new key value pair.
Method 4: Using Objcet.assign() method
In this approach, we are using Objcet.assign() method to assign the key and value to the object. We are passing the object name and the field that we want to use in the object. It assign those fields to the given object.
Method 5: Using Objcet.defineProperty() method
In this approach, we are using Objcet.defineProperty() method to assign the key and value to the object. We are passing the object name and the field that we want to use in the object with some extra specification that is served by the method itself.
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How to Add a Key/Value Pair to an Object in Javascript
Topic: JavaScript / jQuery Prev | Next
Answer: Use Dot Notation or Square Bracket
You can simply use the dot notation ( . ) to add a key/value pair or a property to a JavaScript object.
Let's try out the following example to understand how it basically works:
Alternatively, you can also use the square bracket notation ( [] ) to add a key/value pair to a JavaScript object. The following example produces the same result as the previous example:
The advantage of using square bracket notation is, you can substitute the key inside the square bracket with a variable to dynamically assign a key or property name to an object.
See the tutorial on JavaScript Objects to learn more about creating and manipulating objects.
Related FAQ
Here are some more FAQ related to this topic:
- How to check if a value is an object in JavaScript
- How to remove a property from a JavaScript object
- How to convert JavaScript object to JSON string
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Dot notation. The most common and straightforward way to add a key-value pair to an object is to use the dot notation. You have probably already used this in the past, and it's sufficient in most situations you will encounter. const obj ={a:1}; obj.b=2; obj.c=3;// obj = { a: 1, b: 2, c: 3 }
var myValue = "Petrol"; // Dynamically adding a key/value pair. myCar[myKey] = myValue; console.log(myCar); See the tutorial on JavaScript Objects to learn more about creating and manipulating objects. Here are some more FAQ related to this topic: