JavaScript Number Methods
About This Index
This page is the JavaScript Number Methods index for the tutorial track. Each row links to a full guide with syntax, examples, and FAQs.
Learn what a Number is on /js/number. Use this page when you need a specific API such as toFixed(), toString(), or isInteger().
Start with toFixed(), toString(), isInteger(), and parseInt()—then browse the rest by category.
How to Call a Number Method
Instance methods use a dot; static helpers use Number:
const n = 3.14159;
const rgb = 255;
// Instance (Number.prototype)
n.toFixed(2); // "3.14"
rgb.toString(16); // "ff"
n.toPrecision(3); // "3.14"
n.toExponential(2); // "3.14e+0"
// Static (on Number)
Number.isInteger(5); // true
Number.isNaN(NaN); // true
Number.parseInt("42", 10); // 42
Number.parseFloat("3.14"); // 3.14JavaScript Number Methods Table
All method guides in this JavaScript tutorial series (10 tutorials).
Convert to String
4 methodsTurn numbers into text for display, fixed decimals, significant digits, scientific notation, colors, and base conversion.
| Method | Description | Tutorial |
|---|---|---|
toString() | Return a string for a number in base 2–36 — default decimal, binary/hex via radix, keeps the minus sign for negatives. | Try it |
toExponential() | Format a number in exponential (scientific) notation — optional fractionDigits 0–100 for mantissa precision. | Try it |
toFixed() | Format a number with a fixed count of decimal places — rounds, pads zeros, returns a display string. | Try it |
toPrecision() | Format a number to a chosen count of significant digits — may use plain or exponential form. | Try it |
Static Methods
6 methodsCall on Number itself (not on number instances) to inspect, validate, or parse values.
| Method | Description | Tutorial |
|---|---|---|
isFinite() | Static check: return true only for finite number values — no coercion, rejects Infinity, NaN, and non-numbers. | Try it |
isInteger() | Static check: return true only for integer number values — no coercion, rejects floats, Infinity, NaN, and non-numbers. | Try it |
isNaN() | Static check: return true only for the number value NaN — no coercion, safer than global isNaN(). | Try it |
isSafeInteger() | Static check: return true only for integers in the MAX_SAFE_INTEGER / MIN_SAFE_INTEGER range — no coercion. | Try it |
parseInt() | Static parse: turn a string into an integer with optional radix 2–36 — same as global parseInt. | Try it |
parseFloat() | Static parse: turn a string into a floating-point number — keeps decimals, same as global parseFloat. | Try it |
Frequently Asked Questions
Start with toFixed()
Open the formatting guide—syntax, examples, and FAQs.
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