Basic knowledge of Javascript (1) Core basic syntax and event model_Basic knowledge

1. Javascript core basic syntax

1. Javascript is a programming language that increases interactive effects. It was originally invented by Netscape and was finally submitted to ECMA (European Computer Manufacturers Association). ECMA standardized Javascript and named it Javascript.

2.Javascript is an interpreted language that can run directly under the browser without compilation.

3. What is Javascript used for?

1. You can control all elements in the web page, add, delete and modify the attributes of elements.

2. You can put dynamic text in html.

3. Respond to events generated by users when using web pages.

4. Verify the data entered by the user.

5. Detect the user’s browser.

6. Used to create cookies.

4. Three ways to create Javascript in html web pages

1. External style:

Create a file named: xx.js and link it via in the head or body of html or directly use <script></script> to load

3. Inline style:

Add events directly in the tag:Load

5.Javascript data type:

Its data types have two major categories: 1. Primitive data type 2. Reference data type (object)

Primitive data types: 1.typeof 2.number 3.string 4.boolean 5.null 6.undefined

Reference data types: (There are three predefined objects) 1. Native objects (Object, number, string, boolean, function, Array, Date, etc.) 2. Built-in objects: no need to display initialization (math, Global) 3. Host object (mainly BOM and DOM)

6.BOM and DOM

BOM: Browser Object Model

DOM: Document Object Model

2. Javascript event model

1.Javascript event model: 1. Bubbling type: When the user clicks the button: input-body-html-document-window (bubbles from bottom to top) IE browsing The device just uses bubbling

2. Capture type: When the user clicks the button: window-document-html-body-input (from top to bottom)

After ECMA standardization, other browsers support both types, capture happens first.

2. Three ways of writing traditional events:

1.

2.======<script>function name1(){alert('helloword!');}</script> / /Famous function

3. //Anonymous function

Copy code The code is as follows:

<script><br /> Var button1=document.getElementById("input1");<br /> button1.onclick=funtion(){<br /> alert('helloword!')<br /> }<br /> </script>

3. How to write modern events:

Copy code The code is as follows:

//Add event in IE
<script><br /> var fnclick(){<br /> alert("I was clicked")<br /> }<br /> var Oinput=document.getElementById("input1");<br /> Oinput.attachEvent("onclick",fnclick);<br /> -----------------------------------------------<br /> Oinput.detachEvent("onclick",fnclick);//Delete events in IE<br /> </script>
//Add event in DOM
<script><br /> var fnclick(){<br /> alert("I was clicked")<br /> }<br /> var Oinput=document.getElementById("input1");<br /> Oinput.addEventListener("onclick",fnclick,true);<br /> -----------------------------------------------<br /> Oinput.removeEventListener("onclick",fnclick);//Delete events in DOM<br /> </script>
//Compatible with IE and DOM adding events
<script><br /> var fnclick1=function(){alert("I was clicked")}<br /> var fnclick2=function(){alert("I was clicked")}<br /> var Oinput=document.getElementById("input1");<br /> if(document.attachEvent){<br /> Oinput.attachEvent("onclick",fnclick1)<br /> Oinput.attachEvent("onclick",fnclick2)<br /> }<br /> else(document.addEventListener){<br /> Oinput.addEventListener("click",fnclick1,true)<br /> Oinput.addEventListener("click",fnclick2,true)<br /> }<br /> </script>