Concept

In the JavaScript programming language, comparisons between values are an important part of the programming process. It plays a role in deciding the branching behavior to be performed.

Equal and not equal comparison

Equal (==) comparison is used to check if two values are equal.

var x = 5;
var y = 10;

console.log(x == y);  // false
console.log(x == 5);  // true

The not equal operator (!=) is used to check if two values are different or not.

var x = 5;
var y = 10;

console.log(x != y);  // true
console.log(x != 5);  // false

Strict and non-strict comparison

Strict comparison (===) is used to check if two values are equal and of the same data type.

var x = 5;
var y = '5';

console.log(x === y);  // false
console.log(x === 5);  // true

Non-strict inequality (!==) is used to check if two values are different or different data types. For example:

var x = 5;
var y = '5';

console.log(x !== y);  // true
console.log(x !== 5);  // false

Comparisons

Greater than (>) comparison is used to check if a value is greater than another value. Less than (<) comparison is used to check if a value is less than another value.

var x = 5;
var y = 10;

console.log(x > y);   // false
console.log(x < y);   // true

Greater than or equal to (>=) comparison is used to check if a value is greater than or equal to another value. Less than or equal to (<=) comparison is used to check if a value is less than or equal to another value.

var x = 5;
var y = 10;

console.log(x >= y);   // false
console.log(x <= y);   // true

Logical comparison

In JavaScript, we can combine multiple comparison expressions together to create logical comparison expressions. We have three main logical comparison operators:

• Logical operator && (AND): The result is true if both expressions are true.
• Logical operator || (OR): The result is true if at least one of the expressions is true.
• The operator ! (NOT): The result is true if the expression after it is false.

var x = 5;
var y = 10;
var z = 15;

console.log(x < y && y < z);     // true
console.log(x < y || y > z);     // true
console.log(!(x == y));          // true