JavaScript: Overview

Learning Essentials:

1. What is JavaScript

2. JavaScript features

3. The history of JavaScript

4, the core of JavaScript

Body:

1. What is javascript:

JavaScript was born in 1995. Purpose: Verify data destined for the server side. Increase Web engagement and enhance user experience

The validation of the form before JS does not appear is done on the server side, so the customer experience is very bad. (For example, enter a password: The input is sent to the server side, if the input is not correct, return to the user, re-enter, because the client to the server needs time, that is, customers need twice times the time to know their password input error such a customer experience is not good)

JS is an " explanatory " programming language with object-oriented ability
Programming languages are divided into two main categories: interpreted and compiled.
The interpreted language does not require the compiler to compile. Can be directly executed, directly out of effect
A compiled language requires the compiler to compile and execute the compiled file to produce an effect.

JS is " Object-based " and " event-driven " (select, click, and other events only trigger JS code) and has a relatively secure "client- side scripting language " does not need to run in a specific language environment, only need to have a browser to support his

2. JavaScript Features:
Loose: JS's variable does not have to have a definite type, declare the variable directly with the weak type Var
Object properties: JS maps object names to arbitrary attribute values
Inheritance mechanism: The inheritance mechanism of face object in JS is based on prototype

3. JavaScript history:
Initial embedded scripting language: c--(c-minus-minus) renamed Scripease after----the idea of a script that can be embedded in a Web page is an important cornerstone of the Internet

　　1995 working at the Netscape company Brandon in order to solve the problem of validating before submitting data to the server--Netscape Navigator 2.0 and Sum company jointly developed a scripting language called LiveScript---for marketing convenience-renamed Java Script

Microsoft released IE3 and built a JavaScript to get the cloned version called JScript. Also provide your own VBScript (VBScript is the exclusive client script for IE)

There were 3 different versions of JavaScript Netscape Navigator 3.0 in JavaScript ie in JScript and Cenvi in Scriptease

ECMA (European Association of Computer Manufacturers)
ECMA-262 Standard: Defines the syntax and semantics of scripting languages-called ECMAScript (New scripting language) the standard standardizes the syntax and semantics of a generic, cross-platform, vendor-neutral scripting language

4.JavaScript Core:

The complete JavaScript consists of three parts:
1. Core (ECMAscript)--(He only prescribes syntax, type, statements, keywords, reserved words, operators, objects, etc.) and web browsers have no dependencies
2. DOM (Document Object model)
3. BOM (Browser object model)

Ietest: Tools for testing IE and containers

Mainstream browsers: Microsoft's IE, Netscape Firefox, Google (Google), Apple (Safira), Opera

JavaScript: Overview