Abbreviation :JavaScript-JS   ECMAScript-ES

Let me write it out front : It's not pleasant to nibble at words most of the time , But we have to get past that , Get used to , Let yourself not hate , As for whether you like it or not , Let's wait for the answer .

JavaScript origin JavaScript Born in 1995 year , from Netscape Navigator( Netscape , Hereinafter referred to as Netscape ) The language designed by the company , The purpose is to solve the problem of form input validation at that time ( It was the form validation on the server side ). At that time, Microsoft was in IE3 It also realized JavaScript, But in order to avoid the authorization problem of Netscape , So it's called JScript.JavaScript The predecessor is actually called LiveScript, Later when Netscape released the second version , In order to take advantage of the time Java The heat of the , Temporarily changed to JavaScript. It also makes a lot of people not understand JavaScript People always misunderstood as Java The relatives of , But it doesn't really matter . later , Because Microsoft and Netscape use their own versions of JavaScript, There is no standard set of rules for reference , therefore , stay 1997 year , With JavaScript1.1 The proposal for the blueprint was submitted to the European Computer Manufacturers Association (ECMA,European Computer Manufacture Association). The association designates 39 Technical Committee No. 1 is responsible for this standardization task , After a few months , At last, I finished ECMA-262, It's called ECMAScript New scripting language for . In the second year ,ISO/IEC( International Organization for standardization and International Electrotechnical Commission ).

JS Follow ES, Most of the time we're barking together , We can also not go deep into , But now that I'm in the door , Whether it's out of feelings or a better understanding of the language , I think it is necessary to understand .JS Is a browser based scripting language , and ES It is a standard of scripting language led by European Computer Manufacturing Association .JS Is based on ES A scripting language developed by the standard , image node Is based on ES A background language for standard development .

Browser's JS The implementation of the language consists of three parts :

1.  ES, This is a JS At the heart of , yes JS International standards that must be followed ;

2.  Document object model , That is to say DOM, Mainly used for operation html Element node of ;

3.  Browser object model , That is to say BOM, It's mainly the objects implemented by each browser .

ES

ES It doesn't depend on the browser , It just defines the basic part of scripting language .ES It is stipulated that the language consists of seven parts

grammar 、 type 、 sentence 、 The operator 、 keyword 、 Reserved words 、 object .

These characteristics are similar to java Language is similar to other languages .

ES Version change of :

The first edition , The main basis is JS1.1 To write .

The second edition , Just editing , New features are not implemented .

The third edition , Added something like regular 、 Exception handling and other new features . The release of the third edition marks ES Become a real programming language , This version is the main compatible version in the following ten years .

The Fourth Edition , A lot of changes , abandoned , use 3.1 Version substitution 4.0 You can't send the fifth edition directly , That's the legend ES5.

DOM

Why use DOM? In order to dynamically change the page display . The standard is W3C Set standards , Concrete API And the implementation will be described later .

BOM

Browser object model , Including windows 、 Browser information 、location、screen、cookie、XMLHttpRequst etc. , But there are no standards to follow .

because JS The carrier of operation is different , In the process of working and learning, it is inevitable to encounter all kinds of compatibility problems , Fortunately, most compatibility problems can be solved by Baidu .

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