What is the difference between == and === in JavaScript?

The == operator (loose equality) performs type coercion of operands before comparison.

The === operator (strict equality) does not perform type coercion. It compares both the values and the types of operands.

// Examples of ==
console.log(5 == '5');   // true (the string '5' is coerced to the number 5)
console.log(true == 1);    // true (the number 1 is coerced to true)
console.log(null == undefined); // true (special rule)

// Examples of ===
console.log(5 === '5');  // false (number type is not equal to string type)
console.log(true === 1);   // false (boolean type is not equal to number type)
console.log(null === undefined); // false (null type is not equal to undefined type)

Using === is preferable in most cases because it is more predictable and avoids the implicit behavior associated with type coercion.