JavaScript Comparisons

JavaScript provides various operators to compare values. These comparison operators return Boolean values (`true` or `false`) based on whether the comparison is true or not.

1. Comparison Operators

Here are the primary comparison operators in JavaScript:

- Equal to (`==`)

Checks if two values are equal, with type conversion if necessary:

// Equal to operator
console.log(5 == 5);       // true
console.log(5 == '5');     // true (type coercion)
console.log(5 == 10);      // false

            

- Strict Equal to (`===`)

Checks if two values are equal and of the same type, without type conversion:

// Strict equal to operator
console.log(5 === 5);      // true
console.log(5 === '5');    // false (different types)
console.log(5 === 10);     // false

            

- Not Equal to (`!=`)

Checks if two values are not equal, with type conversion if necessary:

// Not equal to operator
console.log(5 != 10);      // true
console.log(5 != '5');     // false (type coercion)
console.log(5 != 5);       // false

            

- Strict Not Equal to (`!==`)

Checks if two values are not equal and/or not of the same type, without type conversion:

// Strict not equal to operator
console.log(5 !== 10);     // true
console.log(5 !== '5');    // true (different types)
console.log(5 !== 5);      // false

            

- Greater Than (`>`) and Less Than (`<`)< /h3>

Checks if one value is greater than or less than another value:

// Greater than and less than operators
console.log(10 > 5);       // true
console.log(5 < 10);       // true
console.log(10 > 10);      // false
console.log(10 < 5);       // false

            

- Greater Than or Equal to (`>=`) and Less Than or Equal to (`<=`)< /h3>

Checks if one value is greater than or equal to, or less than or equal to another value:

// Greater than or equal to and less than or equal to operators
console.log(10 >= 10);     // true
console.log(5 <= 10);      // true
console.log(10 >= 5);      // true
console.log(10 <= 5);      // false

            

2. Comparison with Type Conversion

JavaScript performs type conversion in some comparisons. Be cautious when using the `==` operator as it can lead to unexpected results:

// Type conversion example
console.log('5' == 5);     // true (string '5' is converted to number 5)
console.log('5' === 5);    // false (different types)
console.log(0 == false);   // true (0 is converted to false)
console.log(0 === false);  // false (different types)

            

3. Comparing Objects

When comparing objects, JavaScript compares references, not the actual contents of the objects:

// Comparing objects
const obj1 = { name: 'John' };
const obj2 = { name: 'John' };
const obj3 = obj1;

console.log(obj1 == obj2);  // false (different references)
console.log(obj1 === obj2); // false (different references)
console.log(obj1 == obj3);  // true (same reference)
console.log(obj1 === obj3); // true (same reference)

            

4. Best Practices

Use the strict equality (`===`) and strict inequality (`!==`) operators to avoid unexpected results caused by type conversion. Always be aware of how JavaScript handles type coercion in comparisons.