JavaScript: How to check whether object has given property or not?

You can use ‘in’ operator to check whether object has given property or not. ‘in’ operator returns true, if the object has given property, else false.

Syntax

propertyNameOrIndexNumber in objectName

propertyNameOrIndexNumber can be property name or array index.

objectName is the object (or) array name.

HelloWorld.js

var hobbies = ["Football", "cricket", "chess", "Trekking"];

var employee = {
  name : "Krishna",
  age : 29
};

var a = 0 in hobbies; //true
var b = 2 in hobbies; //true
var c = 5 in hobbies; //false

var d = "name" in employee; //true
var e = "age" in employee; //true
var f = "id" in employee //false

console.log("a : " + a);
console.log("b : " + b);
console.log("c : " + c);
console.log("d : " + d);
console.log("e : " + e);
console.log("f : " + f);

Output

a : true

b : true

c : false

d : true

e : true

f : false

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