Strict equality (===)

Examples

Strict and loose comparison:

console.log(5 === 5);
console.log(5 === '5');
console.log(5 == '5');

Output:

true
false
true

Oddities of loose comparison:

console.log(0 == '');
console.log(null == undefined);
console.log(null === undefined);

Output:

true
true
false

Objects are compared by reference:

const a = { x: 1 };
const b = { x: 1 };
 
console.log(a === b);
console.log(a === a);

Output:

false
true

Notes

Always use === and !==. Loose == converts types by confusing rules first. The only common exception is value == null, which checks for both null and undefined.