03JavaScript programming practicing the Road 2019-05-19_14-33-19--05-19_15-09-07 js Introduction and basic use of variables and constants

es.md

JavaScript programming practicing the Road 
- pre-knowledge html5 + css3 - Course Outline 
1. The client native JS (ES6 / ES7 / ..) 
2.js popular libraries and other jq 
3. The server-side JS (the Node / Express / KOA) 
4 the front end js framework (VUE / REACT / ..) ... 

- courses to learn the status of js, traveled the world are not afraid, is the web front-end or full-stack web development the most important core technology, directly determine the income and career development 

clients native JavaScript (ES5 / ES6 / ES7 / ...) 
js use of the basic profile 
  html markup language CSS 
  JavaScript (js) client server database programming language 

  js writing position   
      1 is placed at the end of the body element is preferably html page 
          < Script type = "text / JavaScript" > 
             Alert ( " Hello JS " );
           </ Script > 
      2 rows in formula (Learn) 
      3 outer chain (used in the project)
 
 common output statement
       alert ( "content") pop
       the console.log ( "information"); console output 
       document.write ( "..")        
Variables and Constants 
  ES5 var 
  ES6 the let / const      
data types and their conversion 
operator 
arithmetic + - * / ++ -% 
assignment operator = 
relationship> <  > = < = = == === ==!! 
  && ||! 
  :? 
  , 
flow control structure 
+ sequential 
  statements executed from left to right down 

+ selection (branch) 
 IF / IF- the else / Switch 

+ cycle (repeat) 
the while / for / the while-do 
function 
objects 
array of 

strings 

Date / Math / ...

index.js

console.log ( "is available for purchase to Study"); // console output

1getting-start.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <div onclick="alert(123);">hello world</div>
    <script src="./js/index.js">
    </script>
    <script type="text/javascript">
        alert("hello js");
        alert("ok");
    </script>
</body>
</html>

2printMessage.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <!--mmmm -->
    <Script > 
        / *   
        Alert ( "the ok"); 
        Alert (123); 
        * / 
       // console.log () 
       // console.log ( "Guess where I'm here"); 
       // document.write ( "ha ha good like JS "); 
       document.write ( " <h1> ha ha good like JS </ h1> " );
     </ Script > 
</ body > 
</ HTML >

3variable.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
        /*A variable whose value may change 
            var variable name = value; 
            
            the variable name 1 alphanumeric characters and underscores $ 
                  2 Do not start with a number 
                  3 can not be a keyword var if else for while ...... 
                  from 4 professional name recommended 
                  5 recommendations camel named from the second word capitalized 
        * / 
        
        / * 
        var the X-; // declare a variable 
        x = 20; // assign values to variables 
        * / 
        var the X- =  20 ; // 20 constants 
        var A, b, c;
         var studentAge =  20 ;
         var Sex =  " M " ;
         // var 3D; error 
        //var  %4; 错误
        alert(x);
    </script>
</body>
</html>

03JavaScript programming practicing the Road 2019-05-19_14-33-19--05-19_15-09-07 js Introduction and basic use of variables and constants

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