This post explores what are the differences between the in
and hasOwn()
in Javascript.
Even if they are both used for checking if an object has a given property, the biggest difference between these two is that in
will return true for inherited properties, whereas hasown()
will return false for inherited properties.
Let's seen an example:
class Human {
name
}
class Employee extends Human {
salary
}
const obj = new Employee()
console.log("salary" in obj) // true
console.log(Object.hasOwn(obj, "salary")) // true
console.log("name" in obj) // true
console.log(Object.hasOwn("name")) // false
A few notes:
- the
hasown()
method comes as a replacement for the olderhasOwnProperty()
. More details in this StackOverflow thread. - the
in
operator works also to check if private properties are set on a Js object. Of course, this assumes that the check is done inside of the class that contains that private property.
You can find here more details about the hasown()
method and here more details about the in
operator.
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📖 50 Javascript, React and NextJs Projects
Learn by doing with this FREE ebook! Not sure what to build? Dive in with 50 projects with project briefs and wireframes! Choose from 8 project categories and get started right away.