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

== vs ===

Both == and === check the types of their operands. The difference is in how they respond if the types don't match. The == allows coercion when types don't match and === disallows coercion.

1// == Examples (loose equality)
25 == "5"    // true (string "5" is converted to number 5)
30 == false  // true (false is converted to number 0)
4null == undefined  // true
5[] == false // true (both are converted to 0)
6
7// === Examples (strict equality)
85 === "5"    // false (different types)
90 === false  // false (different types)
10null === undefined  // false
11[] === false // false

As a best practice, it's generally recommended to use === because:

• It's more predictable since no type conversion occurs
• It helps prevent subtle bugs caused by unexpected type coercion
• It makes your code's intentions clearer

Always use triple equals, ===, unless you have a specific reason to use ==. The only time you might want to use == is when you specifically want type coercion, but those cases are rare and should be clearly documented.