Как проверить существование свойства в объектк js и избежать ошибки "Cannot Read Property of Undefined"?
const obj = { name: "Pedro Homes", age: 99, address: { street: "Av. Pdte. Ibáñez", city: "Puerto Montt", state: "Los lagos" } }; // Comparing with undefined console.log(typeof obj.name) console.log(typeof obj.sex) // Check if "name" property exists in obj if ("name" in obj) { console.log("Property 'name' exists in obj"); } // Check if "name" property exists in obj if ("name" in obj) { console.log("Property 'name' exists in obj"); } // Check if "sex" property exists in obj if ("sex" in obj) { console.log("Property 'sex' exists in obj"); } else { console.log("Property 'sex' does not exist in obj"); } // if object has specified property console.log(obj.hasOwnProperty('name')); // => true console.log(obj.hasOwnProperty('sex')); // => false