Originally published on php-to-js.learnio.dev — part of the PHP to JavaScript course. View this lesson on the original site.

Use `===` the same way you learned in modern PHP

If you already prefer === in PHP, keep that habit in JavaScript. Loose == exists in both languages and surprises people who expect “same value” without remembering coercion rules.

PHP habit

<?php
var_dump('5' == 5);       // true  — string coerced to number
var_dump('5' === 5);      // false — type and value must match

var_dump(0 == false);     // true
var_dump(0 === false);    // false

var_dump(null == undefined); // not applicable in PHP

JavaScript equivalent

console.log('5' == 5);      // true
console.log('5' === 5);    // false

console.log(0 == false);    // true
console.log(0 === false);   // false

console.log(null == undefined);  // true  — special case in JS
console.log(null === undefined); // false

Operator	Coerces types?	Use in new code?
`===` / `!==`	No	Yes — default
`==` / `!=`	Yes	No — code review should question it

Traps that only bite with `==`

console.log('' == 0);          // true
console.log([] == false);        // true
console.log('5' == 5);         // true
console.log(null == undefined); // true

None of these are true with ===. After the truthy lesson, you can see why: == leans on coercion and truthiness, not plain equality.

PHP and JS agree on the habit

Teams on PHP 8+ and modern JavaScript share the same rule: strict comparison by default, loose only when you document why.

Try it

Use the amber Try it panel below. Click Run.

const pairs = [
  ['5', 5],
  [0, false],
  ['', 0],
  [null, undefined],
];
for (const [a, b] of pairs) {
  console.log(JSON.stringify(a), '==', JSON.stringify(b), a == b, '===', a === b);
}

Read the two boolean columns. Your default in new code should match the === column.

From PHP to JavaScript — JavaScript Syntax Foundations for PHP Devs

Use === the same way you learned in modern PHP