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Include properties conditionally

Written byPhuoc Nguyen
28 Aug, 2023
To define a property of an object in JavaScript, we typically declare it directly. For example:
const obj = {
foo: 'Baz',
bar: 'Qux',
Here's an example: we have an object with two properties named `foo` and `bar`, which have the values `Baz` and `Qux`, respectively.
Now, let's say we only want to include the `bar` property if a certain condition is met. The standard approach is to declare the object as a variable using the `let` declaration, and then set the property later.
let obj = {
foo: 'Bar',
if (condition) {
obj.bar = 'Qux';
While the `if` statement approach works, it's not so convenient when we have to conditionally set many properties at once. Additionally, it turns the object from immutable to mutable due to the `let` declaration.
Fortunately, JavaScript offers the object spread syntax, which is quite handy in this scenario. It allows us to selectively include properties from the source objects, depending on our conditions.
To simplify the sample code above, we can use the following code:
const obj = {
foo: 'Baz',
...(condition && { bar: 'Qux' }),

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Phước Nguyễn