Doing the maths

JavaScript does the maths you know from school, with the usual order: * and / before + and -, and parentheses first. All numbers share one type, number, whether they're whole or have decimals.

Some sums have no sensible answer. Instead of crashing, JavaScript gives a special value and carries on, so a typo can quietly spread through your sums.

7 + 2    // 9
7 - 2    // 5
7 * 2    // 14
7 / 2    // 3.5
7 % 2    // 1  - remainder after dividing
2 ** 3   // 8  - 2 to the power 3
5 / 0    // Infinity
0 / 0    // NaN - "Not a Number"

• % gives the remainder: handy for "is this number even?" (n % 2 === 0).
• ** raises to a power.
• NaN is what you get from maths that makes no sense. Its type is still "number".