define 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!==

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

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:

0. GreetingTurn over their own blog, the last one is June 26, said the update? Review just past this July, all day is the company's induction training plus their own small papers, every day to fight to 1 o'clock in the morning more, this is to hang

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 it involves the implementation principle of undefined. So, after thinking about it, write down

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

Used in JScript to represent undefined undefinedWhat exactly does an identifier mean undefined? IT and "undefined" What are the differences and connections (including "included")? Why sometimes can use undefined to compare with variable, and