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

=== (strict equality) checks that both value and type are identical without coercion. == (loose equality) converts operands to a common type before comparing them, producing unexpected matches.

In JavaScript, equality checks come in two varieties: strict (=== and !==) and loose (== and !=). Strict equality compares two values without type conversion: if the operand types differ, the comparison returns false immediately.

Loose equality (==) performs implicit type coercion when comparing operands of different types. For example, '42' == 42 evaluates to true because JavaScript converts the string into a number. It also leads to counter-intuitive cases where false == 0 is true and null == undefined is true.

In test automation, loose equality is a frequent source of false-positive checks. Text retrieved from the DOM is always a string. Comparing '0' == false passes with loose equality but masks a logic defect. Modern test code standardizes strictly on ===.

strict-equality.mjs(node)

const str = '100';
const num = 100;

console.log(str == num);
console.log(str === num);
console.log(null === undefined);

Output

true
false
false

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You read a discount code status from the page: const active = '0'. What do active == false and active === false evaluate to?

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

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