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JavaScript offers both basic and static number methods to perform operations on, manipulate, and analyze numeric values.
These methods can be called on any number or Number object.
Converts a number to a string, optionally specifying a radix (base).
let num = 42;
console.log(num.toString()); // "42"
console.log(num.toString(2)); // "101010" (binary)
console.log(num.toString(16)); // "2a" (hexadecimal)
Returns a string representing the number in exponential notation with a specified number of digits after the decimal point.
let num = 123.456;
console.log(num.toExponential()); // "1.23456e+2"
console.log(num.toExponential(2)); // "1.23e+2"
Formats a number with a fixed number of digits after the decimal point.
let num = 3.14159;
console.log(num.toFixed(2)); // "3.14"
console.log(num.toFixed(0)); // "3"
Formats a number to a specified total number of significant digits.
let num = 123.456;
console.log(num.toPrecision(4)); // "123.5"
console.log(num.toPrecision(2)); // "1.2e+2"
Returns the primitive numeric value of a Number object.
let num = new Number(42);
console.log(num.valueOf()); // 42
console.log(typeof num); // "object"
console.log(typeof num.valueOf()); // "number"
These methods are called on the Number constructor, not individual numbers.
Checks if a value is a finite number (not Infinity, -Infinity, or NaN).
console.log(Number.isFinite(42)); // true
console.log(Number.isFinite(Infinity)); // false
console.log(Number.isFinite(NaN)); // false
console.log(Number.isFinite("42")); // false
Checks if a value is an integer.
console.log(Number.isInteger(42)); // true
console.log(Number.isInteger(42.0)); // true
console.log(Number.isInteger(42.5)); // false
console.log(Number.isInteger("42")); // false
Checks if a value is NaN. Unlike the global isNaN(), it does not convert non-numbers.
console.log(Number.isNaN(NaN)); // true
console.log(Number.isNaN(42)); // false
console.log(Number.isNaN("NaN")); // false
console.log(Number.isNaN(undefined)); // false
Checks if a value is an integer within the safe range (Number.MIN_SAFE_INTEGER to Number.MAX_SAFE_INTEGER).
console.log(Number.isSafeInteger(42)); // true
console.log(Number.isSafeInteger(9007199254740992)); // false
console.log(Number.isSafeInteger(42.5)); // false
console.log(Number.isSafeInteger("42")); // false
Parses a string and returns an integer, optionally specifying a radix.
console.log(Number.parseInt("42")); // 42
console.log(Number.parseInt("42.5")); // 42
console.log(Number.parseInt("1010", 2)); // 10 (binary)
console.log(Number.parseInt("abc")); // NaN
Parses a string and returns a floating-point number.
console.log(Number.parseFloat("3.14")); // 3.14
console.log(Number.parseFloat("42")); // 42
console.log(Number.parseFloat("3.14abc")); // 3.14
console.log(Number.parseFloat("abc")); // NaNThese methods can be called directly on a number:
| Method | Description | Example |
|---|---|---|
toString() | Converts a number to a string | (123).toString(); // "123" |
toExponential(n) | Returns a string in exponential notation with n decimals | (1234).toExponential(2); // "1.23e+3" |
toFixed(n) | Formats a number with n decimal places | (3.14159).toFixed(2); // "3.14" |
toPrecision(n) | Formats a number to n significant digits | (3.14159).toPrecision(3); // "3.14" |
valueOf() | Returns the primitive value of a number | (123).valueOf(); // 123 |
These methods are called on the Number object, not on individual numbers:
| Method | Description | Example |
|---|---|---|
Number.isFinite(value) | Checks if a value is a finite number | Number.isFinite(10); // true |
Number.isInteger(value) | Checks if a value is an integer | Number.isInteger(10.5); // false |
Number.isNaN(value) | Checks if a value is NaN | Number.isNaN(NaN); // true |
Number.isSafeInteger(value) | Checks if a value is a safe integer | Number.isSafeInteger(9007199254740991); // true |
Number.parseInt(string) | Converts a string to an integer | Number.parseInt("123abc"); // 123 |
Number.parseFloat(string) | Converts a string to a floating-point number | Number.parseFloat("3.14abc"); // 3.14 |