JavaScript Number 参考

JavaScript 数字

JavaScript 只有一种数字类型。

数字可以带小数，也可以不带小数：

let x = 3.14; // A number with decimals
let y = 34; // A number without decimals

特大或特小的数字可以用科学（指数）表示法书写：

let x = 123e5; // 12300000
let y = 123e-5; // 0.00123

有关 JavaScript 数字的教程，请阅读我们的JavaScript 数字教程。

Name	Description
constructor	Returns the function that created JavaScript's Number prototype
EPSILON	Returns the difference between 1 and the smallest number greater than 1
isFinite()	Checks whether a value is a finite number
isInteger()	Checks whether a value is an integer
isNaN()	Checks whether a value is Number.NaN
isSafeInteger()	Checks whether a value is a safe integer
MAX_SAFE_INTEGER	Returns the maximum safe integer in JavaScript.
MIN_SAFE_INTEGER	Returns the minimum safe integer in JavaScript
MAX_VALUE	Returns the largest number possible in JavaScript
MIN_VALUE	Returns the smallest number possible in JavaScript
NaN	Represents a "Not-a-Number" value
NEGATIVE_INFINITY	Represents negative infinity (returned on overflow)
POSITIVE_INFINITY	Represents infinity (returned on overflow)
parseFloat()	Parses a string an returns a number
parseInt()	Parses a string an returns a whole number
prototype	Allows you to add properties and methods to an object
toExponential(x)	Converts a number into an exponential notation
toFixed(x)	Formats a number with x numbers of digits after the decimal point
toLocaleString()	Converts a number into a string, based on the locale settings
toPrecision(x)	Formats a number to x length
toString()	Converts a number to a string
valueOf()	Returns the primitive value of a number

所有数字方法都会返回一个新值。它们不会改变原始值。