Number Reference / Utilities

JavaScript provides the Number object, which includes properties and methods to work with numeric values. These utilities are divided into static properties/methods (accessed via Number) and instance methods (called on number values).

Note: All number methods return a new value. They do not modify the original number.

Number Properties

These are static properties of the Number object, accessed as Number.<property>.

Property	Description	Example
constructor	Returns the function that created the Number prototype (usually Number)	(123).constructor === Number; // true
EPSILON	Smallest difference between 1 and the next representable number	Number.EPSILON; // 2.220446049250313e-16
MAX_VALUE	Largest finite number in JavaScript	Number.MAX_VALUE; // 1.7976931348623157e+308
MIN_VALUE	Smallest positive number greater than 0	Number.MIN_VALUE; // 5e-324
MAX_SAFE_INTEGER	Largest integer that can be safely represented	Number.MAX_SAFE_INTEGER; // 9007199254740991
MIN_SAFE_INTEGER	Smallest integer that can be safely represented	Number.MIN_SAFE_INTEGER; // -9007199254740991
POSITIVE_INFINITY	Represents positive infinity	Number.POSITIVE_INFINITY; // Infinity
NEGATIVE_INFINITY	Represents negative infinity	Number.NEGATIVE_INFINITY; // -Infinity
NaN	Represents “Not-a-Number”	Number.NaN; // NaN
prototype	Allows adding properties or methods to all Number instances (use cautiously)	Number.prototype.customMethod = function() { … }

Static Number Methods

These are called on the Number object itself:

Method	Description	Example
Number.isFinite(value)	Returns true if the value is finite (not Infinity, -Infinity, or NaN)	Number.isFinite(123); // true
Number.isInteger(value)	Returns true if the value is an integer	Number.isInteger(42.5); // false
Number.isNaN(value)	Returns true if the value is exactly NaN	Number.isNaN(NaN); // true
Number.isSafeInteger(value)	Returns true if value is a safe integer	Number.isSafeInteger(9007199254740992); // false
Number.parseFloat(string)	Parses a string and returns a floating-point number	Number.parseFloat("3.14"); // 3.14
Number.parseInt(string, [radix])	Parses a string and returns an integer	Number.parseInt("1010", 2); // 10

Instance Number Methods

These methods are called on number values or Number objects:

Method	Description	Example
toExponential(fractionDigits)	Converts a number to exponential notation	(1234).toExponential(2); // "1.23e+3"
toFixed(digits)	Formats a number with a fixed number of decimal places	(3.14159).toFixed(2); // "3.14"
toLocaleString([locales, options])	Converts a number to a string formatted according to locale	(123456.789).toLocaleString('en-US'); // "123,456.789"
toPrecision(precision)	Formats a number to a specified total number of significant digits	(123.456).toPrecision(4); // "123.5"
toString([radix])	Converts a number to a string in the specified base	(255).toString(16); // "ff"
valueOf()	Returns the primitive numeric value	new Number(42).valueOf(); // 42