Day50 Initial knowledge of JavaScript

First, Background introduction

(i) Three styles of web development:

Structure: HTML: Describing the structure of a page from a semantic perspective

Style: CSS: From an aesthetic perspective, describe the style (beautify the page)

Behavioral (dynamic) JavaScript: Describe behavior from an interactive perspective (for improved user experience)

(b) Brandon? IKE (Brendan eich,1961-now), invented JavaScript in Netscape in 1995.

(iii) The relationship between JavaScript and ECMAScript

Ecmascript:ecmascript is a standard developed by ECMA International (formerly the European Association of Computer manufacturers, the English name is European Computer Manufacturers Association). ECMAScript is not a language, but a standard.

Part of javascript:

Including JS syntax standard: ECMAScript, DOM, BOM these three parts.

• The grammatical standard of ecmascript:javascript. Includes variables, expressions, operators, functions, if statements, for statements, and so on.
• DOM: An API that operates on elements on a Web page. For example, let the box move, color change, Carousel diagram and so on.
• BOM: An API for manipulating browser-part functionality. For example, let the browser automatically scroll.

(iv) Features:

JavaScript is easy to learn, he is better for beginners, and it is a weakly typed variable language.

Defining a variable requires only: var a:

JavaScript does not care about other things (such as memory release, pointers, etc.) and is more concerned about its business.

Characteristics:

(1) Easy to use: can be written with any text editing tools, only the browser can execute the program.

(2) Interpreting execution (it is an explanatory language ): does not compile beforehand, executes line by row, does not need strict variable declaration.

(3) Object-based: Built in a large number of ready-made objects, writing a small number of programs can accomplish goals

Day50 Initial knowledge of JavaScript