JavaScript Numbers & Math
JavaScript has a single number type covering both whole numbers and decimals.
There is no separate integer type, unlike most other languages.
Every number is stored the same way, which explains several of its quirks.
Example
javascript
const whole = 42;
const decimal = 3.14;
console.log(typeof whole);
console.log(typeof decimal);Both report number.
42 and 3.14 are both of type number.
Numbers are written without quotes.
Very large or very small numbers can use exponent notation.
Syntax
javascript
const count = 42;
const price = 19.99;A number in quotes is a string, not a number.
The usual operators all work as you would expect.
Example
javascript
console.log(10 + 3);
console.log(10 - 3);
console.log(10 * 3);
console.log(10 / 3);Division always produces a decimal when it does not divide evenly.
% gives the remainder, which is how you test for even numbers.
** raises to a power.
Example
javascript
console.log(10 % 3);
console.log(10 % 2 === 0);
console.log(2 ** 10);The output is 1, true, 1024.
Dividing by zero gives Infinity rather than throwing an error.
This surprises people coming from other languages.
Example
javascript
console.log(10 / 0);
console.log(-10 / 0);
console.log(typeof Infinity);Infinity is a number value, like any other.
e means times ten to the power of.
Example
javascript
const big = 1.5e6;
const small = 1.5e-3;
console.log(big);
console.log(small);The output is 1500000 then 0.0015.
Underscores can be used to group digits; they are ignored by JavaScript.
Example
javascript
const million = 1_000_000;
console.log(million);
console.log(million === 1000000);This is purely for people reading the code.
Complete Example
html
<!DOCTYPE html>
<html>
<head>
<title>JavaScript Numbers</title>
</head>
<body>
<h1>JavaScript Numbers</h1>
<p id="out"></p>
<script>
const price = 19.99;
const quantity = 3;
document.getElementById("out").innerHTML =
"Price: " + price +
"<br>Quantity: " + quantity +
"<br>Total: " + (price * quantity) +
"<br>Is even: " + (quantity % 2 === 0);
</script>
</body>
</html>Run the above example in the Try It Editor.
Try dividing by zero:
Add price / 0 and see Infinity appear.
% gives the remainder.Infinity, not an error.One number type keeps the language simple but causes a few surprises.
Infinity instead of an error is the first of them.
Floating point precision, covered shortly, is the biggest.