The in-operator is used to check whether a property within an object with a particular interface type exists or not.
interface ILaptop {
brand : string;
user? : string;
year? : number;
}
let laptop1 : ILaptop = {
brand : "Dell",
}
function nameOfLaptop(obj : ILaptop) {
if ("brand" in obj) {
console.log(obj.brand)
}
}
nameOfLaptop(laptop1)
As you can see the “brand” property does exist within the above object with the type ILaptop and thus the brand of that object will be printed on the terminal screen!
