null undefined

There are two primitive types in javascript: null and undefined. These two types often make JavaScript developers confused, when is null, and when is undefined?The undefined type has only one value, which is undefined. When the declared variable has

Vara; varb !! A; a is undefined by default .! A is true ,!! A is false, so the value of B is false, instead of undefined or other values. It is mainly used to facilitate subsequent judgment .!! It is generally used to forcibly convert the following

In fact, the original ECMAScript types include Undefined and Null. Both types correspond to their own unique private values, namely, undefined and null. A general answer: In fact, the original ECMAScript types include Undefined and Null. Both types

JavaScript Overview 1.1 What is javascript:JavaScript (JS) is a client-side scripting language that is Object-and event-driven and has relative security. It is also widely used as a scripting language for client Web development, and it is often used

The selector's first glimpse into the code architecture:The jquery selector can be divided into five categories according to the type of incoming data: Incoming string: $ ("div"), $ ("#id"), $ (". Div1"), $ (". Div p.title") Incoming

A deep understanding of javascript null and undefined Javascript has two easily overlooked problems: null = undefined and null! = Undefined. In javascript, the syntax stipulates that = is to determine whether the value is equal, and = is to

1, a function contains a set of statements that specify the behavior of an object, which is also an object, called a function object. The function object is connected to the Function.prototype ( the prototype object itself is connected to the Object.

"Data structure and algorithm JavaScript description"--An array reading guide:This article is relatively long, introduced the array of common operation methods and some considerations, and finally a few classic exercises (interview

1. Shallow copy vs deep copyThe copy in this article can also be referred to as a copy, which in this article is considered to be the same meaning of copy and copy. In addition, this article only discusses the replication of complex data types in JS

ObjectiveLong ago, it was common to think that JavaScript was doing some web effects and dealing with events.There are some old stubborn ones around me. NET programmers are still stuck in this perception, and they feel that no backend development is

JQuery static method type usage and source code analysisJQuery. the type method is a tool method for detecting data types. Before analyzing its usage, summarize the methods that js provides for us to monitor data types; i. below is the test code var

1. Use JavaScript 1, elements in HTML defines the following 6 properties:Async: Optional, asynchronous download of external script files.CharSet: optional, by specifying the character set of the code through the SRC attribute, most browsers ignore

The development speed of the front-end technology is obvious to all, JS's ECMA standard is no longer 3 of the world, but no matter how hinting, the basic grammar still has to know the new. Whether you are beginners or many years JS programmer, you

1. Everything in JS (variables, function names, operators, etc.) is case-sensitive. --true is a Boolean value, and true is just an identifier.2. The JS statement ends with a semicolon, but is not required for the reason:A. No semicolon at the end

1. Identifiers:An identifier is the name of a variable, function, property, or parameter of a function.Naming rules for identifiers:(1) The first character must be a letter, underscore, or dollar sign(2) Other characters can be letters, underscores,

Author: nuysoft/high cloud QQ: 47214707 EMail: nuysoft@gmail.com Disclaimer: This article is an original article. If you need to reprint it, please indicate the source and retain the original article link. Read, write, or something wrong. Please

This is the last article in the expression series from simple to deep, but recently the team has been busy and never been busy! However, if you like expressions, please rest assured that some basic principles of Javascript are common in your work,

ECMAScript5 New Array method seems to be relatively simple in fact, there are some details need to understandFirst of all, these methods are not used in the original array, followed by the processing of the sloppy array.(1) These methods do not

This article mainly introduces operators and descriptions in JavaScript. This article describes the Judgment Rules of operators and the Judgment Rules of operators. If you need them, you can refer to JavaScript, = and = can be used to determine

This article is the Reading Notes of the first chapter of situ's javascript framework design. It records what you think is important and shares it with you. 1. namespace: The namespace in js is extended using the object attributes. For example, if