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Conditions and loops

if / else, switch, for, for…of, while, and the ternary operator.

Runs in Zerethon IDE · Node.js 22 Official JavaScript documentation ↗
main.js 
for (let n = 1; n <= 4; n++) {
  if (n % 2 === 0) {
    console.log(n, 'even');
  } else {
    console.log(n, 'odd');
  }
}

for (const fruit of ['apple', 'pear']) console.log(fruit);

const scores = { ada: 90, alan: 85 };
for (const [name, score] of Object.entries(scores)) {
  console.log(`${name}: ${score >= 88 ? 'A' : 'B'}`);
}

let i = 0;
while (true) {
  if (++i > 2) break;
  console.log('i =', i);
}

Output

1 odd
2 even
3 odd
4 even
apple
pear
ada: A
alan: B
i = 1
i = 2

Watch out: for…in walks an object's keys (as strings), not an array's values — use for…of for arrays.

Related topics

Official references