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JavaScript ?? ??

JavaScript ??? ??? ?? ??? ? ??? ??, ??, ??, ?? ??? ?? ???? ? ?????.

var ???? ?? ?? ??(??):

var ?? ??;

JavaScript ?? ?? ??

?? ??? ??(a-z, A-Z) ?? ?? _? ?????. ??? ??, ??, ??? ? ? ??? ??? ? ? ????. ?? ?? ??? ????? ?????.

?? ?? ??? ?????.

var_char
varChar
_varChar
char5

Tips

?? ?? ??? ???? ?? ??? ?? ??? ???? ??? ???? ?? ????. , ?: my_name ?? myName ??.

JavaScript ?? ??

??? ???? ?? ??? ?? ??? ? ????.

var my_name = "Jack" // ????? ?? ??? ?? ??
var number = 2; / ?? ??

?? JavaScript? ??? ?? ???? ?? ??? ?? ?? ???? ?? ?????.

my_name = "Jack";
number = 2;

??? ??? ??? ????. ???? ????? ??? ?? ???? ?? ?? ????? ?????. 

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>php中文網(wǎng)(php.cn)</title> 
    <script type="text/javascript">
    var a = 3;
    var b = 4+a;
    window.alert(b);
    </script>
</head>
<body>
</body>
</html>

??? ?, ?? ??

??? ??? ?? ??? ??? ? ????. ???? var? ???? ??? ???? ??? ?????.

var lastname="Doe", age=30, job="carpenter";

? ???? ?? ?? ?? ?? ?? ????:

var lastname=" Doe" ,
age=30,
job="??";

? = ???? ??

??? ??????? ?? ?? ??? ???? ??? ????. ? ?? ??? ??? ?? ??? ???? ????.

?? ???? ???? carname ??? ?? ???? ????.

var carname;

JavaScript arithmetic

= ? +? ?? ???? ???? JavaScript ??? ?? ??? ??? ? ????. 

<!DOCTYPE html>
<html>
<head> 
<meta charset="utf-8"> 
<title>php中文網(wǎng)(php.cn)</title> 
    <script type="text/javascript">
    var a = 3;
    var b = 4+a;
    window.alert("b =" + b);
    </script>
</head>
<body>
</body>
</html>


???? ??
||
<!DOCTYPE html> <html> <head> <meta charset="utf-8"> <title>php中文網(wǎng)(php.cn)</title> <script type="text/javascript"> var my_name = "Tom"; var age = 18; alert("我的名字叫" + my_name + "，我今年" + age + "歲。"); </script> </head> <body> </body> </html>