How to conditionally add a member to an object using JavaScript ?
Objects are the most important data-type and are building blocks for modern JavaScript. They are different from primitive data-types such as String, Number, Boolean, null, etc. But we can make these datatypes as objects by using the new keyword. There are two approaches to conditionally add a member to an object.
Method 1: This method involves checking if the required condition is true and based on that a property is added to the object.
Example: In this example, if the condition is true then ‘b’ will be added as a member to ‘a’, otherwise not.
Javascript
// Define the object var a = {}; // Check if the condition // is satisfied if (someCondition) { // Add the required // property to the object a.b = 7; } |
Output:
-
When condition is satisfied:
{b: 7} -
When condition is not satisfied:
{}
This approach can also be used in an idiomatic way, using a ternary operator.
Example: In this example, if the condition is true then ‘b’ will be added as a member to ‘a’, otherwise not.
Javascript
var a = { // Use the ternary operator to check // if the property should be added // to the object b: (someCondition? 7 : undefined) }; |
Output:
-
When condition is satisfied:
{b: 7} -
When condition is not satisfied:
{b: undefined}
Method 2: This method is used to add several members to an object. The jQuery library function $.extend() is used for this method. This however does not copy undefined properties to the object.
Example:
Javascript
var newObject = $.extend({}, { a: conditionA ? 7 : undefined, b: conditionB ? 9 : undefined, // More properties as required }); |
Output:
-
When the first condition is satisfied:
{a: 7} -
When both conditions are satisfied:
{a: 7, b: 9}
