if function exists javascript

Directory1 History 2 clarifying misunderstandings 3 basic concepts 4 features 5 different from Java 6 development toolsHistoryProbably in 1992, a company called Nombas began developing an embedded scripting language called C-minus (C-minus-minus, or

Ask for a question. if the user name exists during registration, it will not be successfully registered. in this case, the user name can still be registered. Script $ (function () {// check whether the user name exists $ ("# name "). blur (function (

There are two ways of defining function expressions: function declarations and function expressions. The function declaration is as follows: function functionname (arg0,arg1,arg2) { //functions Body } First is the function keyword,

Original article: http://blogs.msdn.com/ B /jscript/archive/2007/07/26/scope-chain-of-jscript-functions.aspx In JavaScript, the function scope chain is hard to understand. this is because the scope chain of functions in JavaScript is far from that

Recently, due to work needs, I began to develop some Python things. because I have been using Javascript before, I will unconsciously use some Javascript Concepts, syntaxes, and so on. I think it is necessary to summarize the differences between

JS Native judge whether the DOM node exists in the pageThe JavaScript native function does not provide a way to judge whether a DOM node exists, and we usually get DOM nodes that are almost document.getelement. Method, a set of object numbers is

A deep understanding of javascript function parameters and closures, and a deep understanding of javascript Recently I have been studying javascript Functions. functions are the first-class objects of javascript. To learn javascript well, I must

In contrast to C + +, the use of JavaScript in memory has made us more focused on the writing of business logic in development. However, with the continuous complexity of the business, single page applications, mobile HTML5 applications and node.js

Compared with Javascript, Python has recently started to develop some Python things due to work needs. Since Javascript has been used for a long time, it will unconsciously use some Javascript Concepts, syntaxes, and so on, it often falls into a

In the company's image server, the same product will generally have a corresponding large map and thumbnails. Therefore, when we develop the mobile Web site, the default is to use a thumbnail image of the product, to query the database is the path