variable undefined

When discussing the raw data types in JavaScript, most people know the basics from string, number to Boolean. These primitive types are fairly simple and behave in a common sense. However, this article will focus more on the unique raw data types

Js judges the undefined type and js judges the undefined type.Js determines the undefined type if (reValue = undefined){Alert ("undefined "); }The system found that the data could not be determined, and finally found the information to use the

A bad time to answer, especially undefined, because this involves the realization of the principle of undefined. So, after thinking carefully, write down this article, please heroes to shoot bricks. Total known: null = = undefined However: null!==

Exploring undefined in jsBackground If you know Java, you will know that the attributes not assigned in the class will be assigned the initial value by the compiler during compilation. Unlike some static languages such as Java and C #, Javascript is

Detailed analysis of differences between js and undefined, undefined, and null Types This article mainly analyzes and introduces the differences between js undefined type, undefined, null, and NaN. If you need a friend, I hope to help you. Js

Performance improvement and analysis of Web page special effects undefined At work we often need to determine whether a variable/attribute is undefined. There are usually two ways of writing1//Mode 12 typeof age = = ' undefined ';34//Mode 25 Age = =

When discussing the primitive data types in Javascript, most people know the basic knowledge, from String, Number to Boolean. These primitive types are quite simple and behavior is common sense. However, this article will focus more on the unique

Before the cloud-dwelling community sent a similar articleJavaScript null and undefined difference analysisJavaScript undefined,null type and nan value differenceLet's talk about undefined:The variables in JavaScript are weakly typed (I don't need

  This article is mainly on the JS to determine the type of undefined, undefined,null,nan the difference between the detailed analysis of the introduction, the need for friends can come to the reference, I hope to help you. JS judge undefined type

In JavaScript development, I was asked: What is the difference between null and undefined? It is hard to answer at a time, especially undefined, because this involves the implementation principle of undefined. In JavaScript development, I was asked: