Relational Operators in JavaScript

Relational operators test for a relationship such as equal to, less than and so on. Relational operators return true or false depending on whether the relationship exists.

console.log(2 < 3); // true

Equality and Inequality Operators

Equality(==)

Equality(==) operator checks if two values are same. The two operands can be of any type. If two operands are of different types, JavaScript converts both operands to same type and performs the equality check. Let us understand how == operator performs comparison.

If both operands are of same type and if their values are same, then equality(==) operator returns true.

If both operands are of different types, equality(==) operator applies a set of rules to determine equality.

If one value is null and other undefined, they are equal.

console.log(null == undefined); // true

If one value is number and other one a string, the string value is converted to number and then the comparison is performed.

console.log(3 == "3"); // true

If either of the operands is true, it is converted to 1. If the operand is false, it is converted to 0. After that the comparison is performed.

console.log(true == 1); // true
console.log(true == "true"); // false
console.log(false == 0); // true
console.log(false == "false");
false;

In the above example, note that when true is compared with "true", it retured false. In a relational operation, true and false are always converted to numbers.

If either of the operands is an object and other operand is a number or string, the object is converted to a primitive type using valueOf() or toString() method of the object. Then the comparison takes place.

console.log([2, 4, 6] == "2,4,6"); // true

Above statement is true because an array is converted to a string by joining its elements with comma(,).

Strict Equality(===)

Strict Equality(===) operator returns true only if the value and type of both operands are same.

console.log(3 === 3); // true
console.log(3 === "3"); // false

Inequality(!=)

Inequality operator(!=) returns true if both operands are not equal according to equality operator(==).

console.log(3 != 4); // true

Strict Inequality(!==)

Strict Inequality operator(!==) returns true if both operands are not equal according to strict equality operator(===).

console.log(3 !== "3"); // true

Comparison Operators

Comparison operators test the relative order of their operands. Relative order is calculated based on number or alphabets. There are 4 comparison operators.

Less than(<)

The < operator evaluates to true if its first operand is less than the second one. Otherwise it returns false.

console.log(1 < 2); // true
console.log(4 < 1); // false
console.log("A" < "a"); // true

When "A" is compared "a", their ASCII codes are compared. ASCII code of "A" is 65 and of "a" is 97.

Greater than(>)

The > operator evaluates to true if its first operand is greater than the second one. Otherwise it returns false.

console.log(6 > 4); // true

Less than or Equal to(<=)

The <= operator evaluates to true if its first operand is less than or equal to the second one. Otherwise it returns false.

console.log(4 <= 4); // true

Greater than or Equal to(<=)

The >= operator evaluates to true if its first operand is greater than or equal to second one. Otherwise it returns false.

console.log(6 >= 4); // true
console.log(4 >= 4); // true
console.log(3 >= 4); // false