JavaScript in and instanceof operators
JavaScript Relational Operators are used to compare their operands and determine the relationship between them. They return a Boolean value (true or false) based on the comparison result.
JavaScript in Operator
The in-operator in JavaScript checks if a specified property exists in an object or if an element exists in an array. It returns a Boolean value.
let languages = ["HTML", "CSS", "JavaScript"];
// true (index 1 exists in the array)
console.log(1 in languages);
// false (index 3 doesn't exist in the array)
console.log(3 in languages);
Output
true false
const Data = {
name: "Rahul",
age: 21,
city: "Noida"
};
// true ("name" property exists in the object)
console.log("name" in Data);
// false ("gender" property doesn't exist in the object)
console.log("address" in Data);
Output
true false
JavaScript instanceof Operator
The instanceof operator in JavaScript tests if an object is an instance of a particular class or constructor, returning a Boolean value.
let languages = ["HTML", "CSS", "JavaScript"];
console.log(languages instanceof Array);
console.log(languages instanceof Object);
console.log(languages instanceof String);
console.log(languages instanceof Number);
Output
true true false false
let myString = new String();
let myDate = new Date();
console.log(myString instanceof Object);
console.log(myString instanceof Date);
console.log(myString instanceof String);
console.log(myDate instanceof Date);
console.log(myDate instanceof Object);
console.log(myDate instanceof String);
Output
true false true true true false
JavaScript Relational operators – FAQs
How does the < (Less than) operator work?
The < operator returns true if the left operand is less than the right operand; otherwise, it returns false.
How does the > (Greater than) operator work?
The > operator returns true if the left operand is greater than the right operand; otherwise, it returns false.
How does the <= (Less than or equal to) operator work?
The <= operator returns true if the left operand is less than or equal to the right operand; otherwise, it returns false.
How does the >= (Greater than or equal to) operator work?
The >= operator returns true if the left operand is greater than or equal to the right operand; otherwise, it returns false.
How does the == (Equality) operator work?
The == operator compares two values for equality after converting both values to a common type (type coercion). It returns true if the values are equal; otherwise, it returns false.
How does the != (Inequality) operator work?
The != operator compares two values for inequality after converting both values to a common type (type coercion). It returns true if the values are not equal; otherwise, it returns false.
How does the === (Strict equality) operator work?
The === operator compares two values for equality without converting their types. It returns true if the values are equal and of the same type; otherwise, it returns false.
How does the !== (Strict inequality) operator work?
The !== operator compares two values for inequality without converting their types. It returns true if the values are not equal or not of the same type; otherwise, it returns false.
