How to check if an Object has a Property

Question

Suppose we have the following javascript object:

var usersList = {

  Bob: {

    age: 27,

    online: true

  },

  Katie: {

    age: 48,

    online: true

  },

  Chris: {

    age: 19,

    online: true

  }

};

How can we find if a specific property exists in the above object. e.g does Bob exists in the above object ?

Answer 1

JavaScript provides us with two different ways to find out if a property exists in an object. One uses the hasOwnProperty() method and the other uses the in keyword. If we have an object usersList with a property of Chris, we could check for its presence in either of the following ways:

if(usersList.hasOwnProperty("Chris")) {

console.log("user exsits");

} else {

console.log ("user does not exists");

}

similarly you can achieve the same result with in keyword:

if( "Chris" in usersList) {

console.log("user exsits");

} else {

console.log ("user does not exists");

}

Let me know in the comments if you have any confusion.