To find out if a property exists on an object we can use in operator:
var school = {schoolName:"MIT"};
console.log("schoolName" in school); // true because schoolName is an own property on the school object
console.log("schoolType" in school); // false because because we did not define a schoolType property on the school object
// Prints true because the school object inherited the toString method from Object.prototype.
console.log("toString" in school); // true
by Luka Tatarishvili
4 years ago