Detailed explanation of JavaScript numerical methods and properties

This article brings you relevant knowledge about javascript, which mainly introduces issues related to numerical methods and properties in JavaScript, including toSting, toFixed, toPrecision, etc., as follows Let's take a look, I hope it will be helpful to everyone.

[Related recommendations: javascript video tutorial, web front-end]

We know that in JavaScript, Not only do reference types have methods and properties, but the three basic data types of string, number, and boolean also have methods and properties.

Today we are going to compare the properties and properties of literal values ​​(strictly speaking, they should be Number objects). A summary of common methods is helpful for our systematic learning and mastering

Number object methods

All number methods can be used for any type of number (literal, variable or expression)

1. toSting() method

- Returns a numerical value as a string

Example:

var num = 100
var str = num.toString()　　//　变量
var str1 = (99).toString()　　//　字面量
var str2 = (100+99).toString()　　//　表达式
console.log(str)　　//　'100'
console.log(str1)　　//　'99'
console.log(str2)　　//　'199'

2 . toFixed() method

- Returns a string value, which contains a number with the specified number of decimal places (will be rounded)

Parameters: Receives a number indicating precision

Example: 　

var num = 9.656
var num1 = num.toFixed(0)
var num2 = num.toFixed(2)
var num3 = num.toFixed(4)
console.log(num1)　　//　10
console.log(num2)　　//　9.66
console.log(num3)　　//　9.6560

3. toPrecision() method

- Returns a string value, which contains A number with a specified length

Parameter: Receive a number, indicating the total number of digits

Example: 　　　

var num = 9.656
var num1 = num.toPrecision()　　//　省略参数表示原数
var num2 = num.toPrecision(2)
var num3 = num.toPrecision(4)
console.log(num1)　　//　9.656
console.log(num2)　　//　9.7
console.log(num3)　　//　9.656

4. toExponential（ ) Method

- Returns a string value that contains a number that has been rounded and used exponential notation

Parameters: Receives a number, defining the number of characters after the decimal point

Example: 　　　　　　

var num = 9.656
var num1 = num.toExponential(2)　　//　省略参数表示原数
var num2 = num.toExponential(4)
ar num3 = num.toExponential(6)
console.log(num1)　　//　9.66e+0
console.log(num2)　　//　9.6560e+0
console.log(num3)　　//　9.656000e+0

5. valueOf() method

- Return the value as a numerical value

Example: 　　

var num = 100
var num1 = num.valueOf()　　//　变量
var num2 = (99).valueOf()　　//　字面量
var num3 = (100+99).valueOf()　　//　表达式
console.log(num1)　　//　100
console.log(num2)　　//　99
console.log(num3)　　//　199

Note: Basically, this method will not be used for values ​​​​in the code, because the valueOf() method is used internally in JavaScript to convert the Number object into a primitive value

TIPS: All JavaScript data types have valueOf() and toString() methods

Convert variables into numbers

These three JS methods can be used to convert variables into numbers

• Number() method
  

• parseInt() method
  

• parseFloat() Methods

It should be noted that these methods are global methods, not methods of numerical objects

Number object properties (not commonly used)

• MAX_VALUE Returns the maximum number possible in JS

• MIN_VALUE Returns the minimum number possible in JS

• NEGATIVE_INFINITY Indicates negative Infinity

• ##　NaN　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　‖　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　ional in infinity_NaN 　　　　　　　　　　　　　　　　　　　　　　　　　　 　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　  ure                                                                                                           -  
  MAX_VALUE Returns the largest possible number in JavaScript
• MIN_VALUE Returns the smallest possible number in JavaScript
  Example:

var x = Number.MAX_VALUE
var y = Number.MIN_VALUE
console.log(x)　　//　1.7976931348623157e+308
console.log(y)　　　//　5e-324

POSITIVE_INFINITY Represents positive infinity (overflow Return on time)

NEGATIVE_INFINITY Represents negative infinity (return on overflow)

Example:

var x = 1 / 0
var y = -1 / 0
console.log(x)　　//　Infinity
console.log(y)　　　//　-Infinity

NaN Non-number

NaN is a reserved word in JavaScript and represents NaN is an illegal number (not a number)

Example:

var x = 100 / 'apple'
console.log(x)　　//　NaN

Numeric attributes cannot be used for variables

Numeric attributes belong to the JavaScript number object wrapper named number

In layman’s terms, these properties can only be accessed by Number.MAX_VALUE

Example:

var x = 6
var y = x.MAX_VALUE　　//　变量访问
var z = Number.MAX_VALUE　　//　数字对象访问
console.log(y)　　//　undefined
console.log(z)　　//　1.7976931348623157e+308

[Related recommendations:

javascript video tutorial

,

web front end

】

The above is the detailed content of Detailed explanation of JavaScript numerical methods and properties. For more information, please follow other related articles on the PHP Chinese website!