search
HomeWeb Front-endJS TutorialThe simplest implementation method to determine the type of integer in JavaScript

We know that JavaScript provides the typeof operator, so the easiest thing to think of is to use typeof to determine whether it is a number type.

Copy the code as follows:

function isNumber(obj) {
    return typeof obj === 'number'
}

This function has no problem with integers and floating point numbers, but it also returns true for NaN values, which makes people feel uncomfortable. After all, no one will use NaN after using isNumber to judge. Arithmetic operations.

Then improve it and try using Object.prototype.toString.

Copy code code is as follows:

function isNumber(obj) {  
  return Object.prototype.toString.call(obj) === '[object Number]'
  }

This time, if the input is a non-number (NaN or a value that can be converted to NaN), false will be returned

Copy code code is as follows:

function isNumber(obj) {
    return typeof obj === 'number' && !isNaN(obj)
}
isNumber(1)   // true
isNumber(1.2) // true
isNumber(NaN) // false
isNumber( parseInt('a') ) // false

Well, this isNumber is good, but there is an equivalent one, use isFinite to judge

Copy the code as follows:

function isNumber(obj) {
    return typeof obj === 'number' && isFinite(obj)   
}

Up to now, the shortest code for numeric judgment is the third one mentioned in this article that uses the isNaN function. Here is the world's shortest digital judgment web code

Copy the code as follows:

function isNumber(obj) {
    return obj === +obj
}

Returns true for integers and floating point numbers, and returns false for NaN or values ​​that can be converted to NaN.

You don’t understand? Gu~~(╯﹏╰)

Garden friends said that this is not the shortest judgment numeric code in the world, and the parameter obj can be changed to one character. (⊙o⊙) You are right.

By analogy, there is a similar shortest judgment using JS dynamic language features (automatic internal type conversion during operator operation).

Copy the code code as follows:

// 判断字符串
function isString(obj) {
    return obj === obj+''
}
// 判断布尔类型
function isBoolean(obj) {
    return obj === !!obj
}


Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
es6数组怎么去掉重复并且重新排序es6数组怎么去掉重复并且重新排序May 05, 2022 pm 07:08 PM

去掉重复并排序的方法:1、使用“Array.from(new Set(arr))”或者“[…new Set(arr)]”语句,去掉数组中的重复元素,返回去重后的新数组;2、利用sort()对去重数组进行排序,语法“去重数组.sort()”。

JavaScript的Symbol类型、隐藏属性及全局注册表详解JavaScript的Symbol类型、隐藏属性及全局注册表详解Jun 02, 2022 am 11:50 AM

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于Symbol类型、隐藏属性及全局注册表的相关问题,包括了Symbol类型的描述、Symbol不会隐式转字符串等问题,下面一起来看一下,希望对大家有帮助。

原来利用纯CSS也能实现文字轮播与图片轮播!原来利用纯CSS也能实现文字轮播与图片轮播!Jun 10, 2022 pm 01:00 PM

怎么制作文字轮播与图片轮播?大家第一想到的是不是利用js,其实利用纯CSS也能实现文字轮播与图片轮播,下面来看看实现方法,希望对大家有所帮助!

JavaScript对象的构造函数和new操作符(实例详解)JavaScript对象的构造函数和new操作符(实例详解)May 10, 2022 pm 06:16 PM

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于对象的构造函数和new操作符,构造函数是所有对象的成员方法中,最早被调用的那个,下面一起来看一下吧,希望对大家有帮助。

JavaScript面向对象详细解析之属性描述符JavaScript面向对象详细解析之属性描述符May 27, 2022 pm 05:29 PM

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于面向对象的相关问题,包括了属性描述符、数据描述符、存取描述符等等内容,下面一起来看一下,希望对大家有帮助。

javascript怎么移除元素点击事件javascript怎么移除元素点击事件Apr 11, 2022 pm 04:51 PM

方法:1、利用“点击元素对象.unbind("click");”方法,该方法可以移除被选元素的事件处理程序;2、利用“点击元素对象.off("click");”方法,该方法可以移除通过on()方法添加的事件处理程序。

整理总结JavaScript常见的BOM操作整理总结JavaScript常见的BOM操作Jun 01, 2022 am 11:43 AM

本篇文章给大家带来了关于JavaScript的相关知识,其中主要介绍了关于BOM操作的相关问题,包括了window对象的常见事件、JavaScript执行机制等等相关内容,下面一起来看一下,希望对大家有帮助。

foreach是es6里的吗foreach是es6里的吗May 05, 2022 pm 05:59 PM

foreach不是es6的方法。foreach是es3中一个遍历数组的方法,可以调用数组的每个元素,并将元素传给回调函数进行处理,语法“array.forEach(function(当前元素,索引,数组){...})”;该方法不处理空数组。

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

Hot Tools

VSCode Windows 64-bit Download

VSCode Windows 64-bit Download

A free and powerful IDE editor launched by Microsoft

PhpStorm Mac version

PhpStorm Mac version

The latest (2018.2.1) professional PHP integrated development tool

DVWA

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software

Zend Studio 13.0.1

Zend Studio 13.0.1

Powerful PHP integrated development environment

EditPlus Chinese cracked version

EditPlus Chinese cracked version

Small size, syntax highlighting, does not support code prompt function