Introduction to JavaScript Introductory tutorial

1. JavaScript was just beginning to address some of the front-end languages developed by server-side validation. Broadband is not popular in the 90 's, when the user hard to enter a lot of information and submitted to the server, waiting for a long time, wait until the submission is not a successful prompt but some required fields are not filled with warnings, so the major browser companies began to develop their own front-end language, But because many companies have developed their own JavaScript. In order to have a unified standard, only then the ECMAScript.

2. ECMAScript can provide core scripting capabilities for different kinds of hosting environments, so the core scripting language is defined separately from any particular hosting environment. A browser is one of its hosting environments, but it is not the only hosting environment. ECMAScript is just a description that defines all the properties, methods, and objects of the scripting language. Other languages can implement ECMAScript as a benchmark for functionality. As shown in the following:

　　　　　　　　　　　　　　　　　　　　　　　　　　　　

3, a complete javsscript is the following composition:

　　　　　　　　　　　　　　　　　　　　　　　　　　

One of the ECMAScript is as mentioned above.

DOM (Document Object model), whose standards are set by the user.

BOM (Browser object model).

ECMAScript and DOM have corresponding international standards, and current mainstream browsers already support these standards.

However, the BOM does not have international standards, so each browser is handled differently, such as the creation of XMLHttpRequest objects and the acquisition of browser window sizes.

4. JavaScript is a lightweight, interpretive programming language. And it's also an object-based, event-driven scripting language. The most important thing is its platform independence, which only relies on the browser, as long as the browser supports JavaScript, it can be executed correctly.

Most Web sites around the world now use JavaScript, no matter what technology you use in the background (Java PHP). NET), using JavaScript without the exception of the front end. So the outlook for JavaScript is very good.

5, JavaScript is a case-sensitive language. (Var hello and var hello are different variables)

The definition of a marker in JavaScript is that the first character must be an English letter, an underscore, or a $ symbol. The next character can be an English letter, an underscore, or a $ symbol or a number (more numbers). The recommendations are all defined in English.

JavaScript supports two types of annotations: the//Type and/* .... */type.

　　

Introduction to JavaScript Introductory tutorial