1. The first JavaScript

JavaScript is the programming language for the Web.

JavaScript is a lightweight programming language.

JavaScript is programming code that can be inserted into HTML pages.

JavaScript, once inserted into an HTML page, can be executed by all modern browsers.

Why learn JavaScript??

  1. HTMLDefines theContent of web page
  2. CSSDescribes thePage layout
  3. JavaScriptControl of theBehavior of web pages

2. Two uses of JavaScript:

The first: js is written in our script tag

Usually we write it above the body closing tag

    <script></script>
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Second: external reference JS files

    <script src=""></script>
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3. Three JavaScript printing methods:

Print in a web page

Document. The write (” “);

Note: Strings with tag structures can be parsed

    document.write("Hello World!!");
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You can also print HTML tags

    document.write("
      

        I'm the first div tag to print 
      
");
    
    document.write("
      

       
 I am a nested paragraph 

      
");
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Print in the console

The console. The log (” “);

Note: Tag structured strings cannot be parsed

    console.log("Hello World!!!");
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Other functions can also be printed:

Print information:

    console.info("info");
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Typo:

    console.error("error");
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Print warning:

    console.warn("warn"); 
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Popup window

Alert (” “);

Note:Unresolvable The tag structurethestring

willDue to the codetheblockingonlyWhen I hit OKcodeBefore the execution continues

    alert("Windows");
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Tip: In later learning, type more code, use console.log(” “); This will be very helpful for learning JavaScript!!