Javasrcipt using JavaScript in---HTML

Using JavaScript in HTML:

————————————————————————————————————————————————————————

Main content;

First, the use of <script> elements.

Second, embed script and external introduction script.

Third, the impact of document mode on Javasrcipt.

Four, under what circumstances consider disabling JavaScript.

————————————————————————————————————————————————————————

First, the use of <script> elements:

1, the main way to use JavaScript in a Web page is to use the <script> element to achieve. Now the <srcipt> element is a member of the HTML specification, with 6 attributes defined for the <script> element in HTML 4.01:

A, async-optional;

B, CharSet--optional;

C, defer--optional;

D, language--waste;

E, src--optional;

F, type--optional.

—————————————————————————————————————————————————————————

Ii. Embedding scripts and external introduction scripts

There are two ways to use it: the first is to write directly to the HTML page:

<script type= "Text/javascript" >

function Sayhi () {

alert ("Hello");

}

</script>

The code contained within the <script> element will be executed from the top to the next, and the interpreter will interpret a function of a function, and nothing else will change until a function has been interpreted.

The second method: embed the external JS file:

<script type= "Text/javascript" src= "Example.js" ></script>

This will enable the successful introduction of a JS file.

Note that if the JS code is written in the <script></script> element that contains the SRC attribute, the code here is ignored, or the JS file introduced by SRC is executed.

The <script> element is in that position in the HTML tag structure?

The <script> element is between

A few points of doubt:

Everyone knows that the HTML tag is executed from the top to the next line of execution, then the JavaScript tag side in the

The code loads a lot of time very long that would not be, load the time the browser will be blank, the inevitable user experience is poor this is a problem??

There are generally three ways to solve this problem:

1, put the <script> elements on the </body> elements above.

2. Use Lazy Load Properties "defer" Eg:<script type= "Text/javascript" defer= "defer" src= "Example.js" ></script>

3. Asynchronous loading defines the "async" attribute in HTML5.

The <noscript></noscript> tag element prompts the user to turn on the display script in a browser that does not support scripting or a script-disabled browser, and will never appear in a script-enabled browser.

Javasrcipt using JavaScript in---HTML