JavaScript? ???
JS ???
??? ??? ????? ?? ?? ?? ??? ???? ???.
?? ???: +, -, *, /, %, ++, --
A = 10 + 20;
A = 10 – 20;
A = 10 * 20;
A = 10 / 20;
(1) "%" ??? ???, ? ??? ??? ???? ????.
A = 10 % 3; // A = 1, ???? 0? ??? ?? ????? ????.
A = 10 % 2 // A = 0, ???? 0?? ? ???
?? ?? ? ????. (2) "++" + 1 ???, ?? ?? 1
“++”? ???(++i) ?? ???(i++)? ??? ? ????.
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>php.cn</title>
<script>
var a = 1;
var b = 1;
document.write(++a);
document.write("<hr>")
document.write(b++);
</script>
</head>
<body>
</body>
</html>? ??? ??? ?????
++a? ?? ?? ?? ??? a=a+? ?????. ?? 1. ?? ?? ???? ?? ?? ? ??? ?? ?? ? ?? ??? ???? ????? ? ???? ??? a=a+1? ??? ?? ? ???? ?????
(3) "--" ?? 1 ???, 1? ??
"--"? ???(--i) ?? ???(-)? ??? ? ????. ?--).
'--' ??? '++' ??? ?????. ?? ???? ???.
?? ???: =, +=, -=, *=, /=“+= " ?? ???? ??? ?????. ?: a += 10 //?? ? a = a + 10“-=" ?? ? ?? ?????. ?: a -= 10 //?? ? a = a - 10
"*=" ?? ?? ?? ?????. ?: a *= 10 //?? ?, a = a * 10
“/=” ?? ??? ?????. ?: a /= 10 //?? ? a = a / 10
??? ???: +, + =
???? "??" ??? ??? ? ??? ?? ??? ??? ? ????.
<!DOCTYPE HTML> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=utf-8"> <title>php.cn</title> <script> var name = "php.cn"; var str = "歡迎來到"+name; document.write(str); </script> </head> <body> </body> </html>
?? ???: >, <, >=, <=, ==, !=, ===, !==
?? ???? ??? ?? ?(true ?? false)???. A = 10 > 20; ????????? // ?? A=false %2 == 0; // ?? A=true
A = 10%2 == “0” ; // ?? A=trueA = 10%3 != 0; //?? A=true
A = 10%2 === “0”; =false
??:
“="? ?? ?????. ?: a = 10
“==”? ????. ??? ???? ? ??? ?? ?????. ?? ???? true? ????, ??? ??? false? ?????. '==='? ?? ?????. ? ? ??? ???? ??? ?????. ??? ?? ???? true? ????, ??? ??? false? ?????. ?? ???: &&, ||, ! ?? ????? true ?? false?? ? ?? ??? ????. '&&' ?? AND(? ??). ??? ??? ????? ?? true?? ??? true??, ??? ??? ??? false???. ??? AND? ? ??? ??? ??? ? ??? true?? ?????. "||" ?? OR. ??? ??? ? ?? ?? ? ???? ???? true? ????, ??? ??? false? ?????. “!” !true = false , !false = true , !100 = false ?? ???: ?: ?? "?? ???"? ? ?? ????? ?????. ??: ???? ?? 1: ?? 2 ??: ???? 1? ???? 2: ???? 3 ??: ??? true?? ??? ?????. "?? 1"? ?? ??? ???? "?? 2"? ??? ?????. ?? ?? ???? if else? ??? ?????. (??? ??? ?? ??? ??????)<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>php.cn</title>
<script>
//比較字符串?dāng)?shù)值和數(shù)值
var name1 = "520";
var name2 = 520;
document.write(name1==name2);
document.write("<hr>");
document.write(name1===name2)
</script>
</head>
<body>
</body>
</html>
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>php.cn</title>
<script>
//給一個成績
var score=61;
//判斷成績所屬級別
if(score<60){
document.write("對不起，您沒有及格");
}else if (score>=60&&score<70){
document.write("您剛好及格");
}
</script>
</head>
<body>
</body>
</html><!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>php.cn</title>
<script>
var age=79;
if(age<10||age>60){
document.write("您好，您符合我們店的優(yōu)惠條件，今天買東西全場5折");
}else if (age>=10&&age<=60){
document.write("不好意思，您不符合我們店的優(yōu)惠條件，今天買東西不享受折扣");
}
</script>
</head>
<body>
</body>
</html>
