JS Introduction and use

JS is a scripting language that runs on a browser and is a scripting language that is applied to client Web development.

The core of JS is very concise and contains two parts: basic grammatical constructs (operators, control structures, statements) and standard libraries (objects with various functions such as array, Date, math, etc.)

The complete JS consists of three parts:

1, the core of JavaScript (ECMAScript)

2. Document Object Model (dom,document)

3. Browser object Model (BOM Browser object models)

Dom is part of the BOM

Dom-->document-->window

Bom-->window

JS Features: No compilation, interpreted by the JavaScript engine, is a weakly typed language, is Object-based.

JS three ways to quote:

1. In the HTML element event, execute the JS event:

<button onclick = "Console.log (' executed click event ')" > button </button>

2, using the script element, the general script tag placed in the head: The JS code directly placed in the script tag, JS code is executed sequentially;

<script type= "Text/javascript" >    console.log (' executed event 2 '); </script>

3, JS external reference script file, the introduction of an external JS file;

<script src= "Ej1.js" ></script>

JS Introduction and use