JAVASCRIPT

How to tell if an attribute exists on an object

const user = {
    name: "Sicrano",
    age: 14
}

user.hasOwnProperty('name');       // Retorna true
user.hasOwnProperty('age');        // Retorna true
user.hasOwnProperty('gender');     // Retorna false
user.hasOwnProperty('address');    // Retorna false

how to check wether the property exist in a object in java script

if (obj.hasOwnProperty('prop')) {
    // do something
}

test if property exists javascript

const hero = {
  name: 'Batman'
};

hero.hasOwnProperty('name');     // => true
hero.hasOwnProperty('realName'); // => false

check if js property exists in class

myObj.hasOwnProperty(myProp)

Check object property exists or not in js

const user1 = {
	username: "john"
};
const user2 = {
	username: "duo"
    authority: "grepper"
}
// check object property
console.log(user1.hasOwnProperty('authority')); // false
console.log(user2.hasOwnProperty('authority')); // true

check property exists

let person = {
   firstName: 'John',
   lastName: 'Doe'
};

let result = 'firstName' in person; 
console.log(result); // true

result = 'age' in person;
console.log(result); // false
Code language: JavaScript (javascript)

JavaScript check if property exists in Object

const userOne = {
  name: 'Chris Bongers',
  email: 'info@daily-dev-tips.com',
};

const userTwo = {
  name: 'John Do',
};

console.log(userOne.hasOwnProperty('email'));
// Returns: true

console.log(userTwo.hasOwnProperty('email'));
// Returns: false

check property exists

let result = person.hasOwnProperty('firstName');
console.log(result); // true
Code language: JavaScript (javascript)

check if property exists javascript

// the coolest way
const obj = {
 weather: 'Sunny; 
}

if('weather' in obj) {
 // do something 
}

check property exists in object javascript

const employee = {
	id: 1,
  	name: "Jhon",
  	salary: 5000
};

const isSalaryExist = "salary" in employee;
console.log(isSalaryExist); //true

const isGenderExist = "gender" in employee;
console.log(isGenderExist); //false

check property exists

let person = {
   firstName: 'John',
   lastName: 'Doe',
   age: undefined
};

let result = person.age !== undefined;
console.log(result); // false
Code language: JavaScript (javascript)