1. 在HTML中嵌入js
<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>My first proper HTML page</title> </head> <body> <h1>Hello world!</h1> <p>My first web page.</p> <script> var message = "Hello world!"; console.log(message); </script> </body> </html>2. if 语句
<script> var name = "Nicholas"; console.log("Hello " + name); if (name.length > 7) { console.log("Wow, you have a REALLY long name!"); } </script>3. if ... else 语句
<script> var name = "cgl"; console.log("Hello " + name); if (name.length > 7) { console.log("Wow, you have a REALLY long name!"); } else { console.log("Your name isn't very long."); } </script>4. if ... else 一大串
<script> var isSanHeWuOpen = false; // 三和屋开了吗？ var isHeHeGuOpen = true; // 和合谷开了吗？ var isQinMianXuanOpen = true; // 秦面轩开了吗？ if (isSanHeWuOpen) { console.log("秋刀鱼定时"); } else if (isHeHeGuOpen) { console.log("宫保鸡丁饭"); } else if (isQinMianXuanOpen) { console.log("一口香 + 肉夹馍"); } else { console.log("喝西北风"); } </script>5. 用 while 循环数绵羊
<script> var sheepCounted = 0; while (sheepCounted < 10) { console.log("I have counted " + sheepCounted + " sheep!"); sheepCounted++; } console.log("Zzzzzzzzzzz"); </script>6. 用 for 循环数绵羊
<script> for (var sheepCounted = 0; sheepCounted < 10; sheepCounted++) { console.log("I have counted " + sheepCounted + " sheep!"); } console.log("Zzzzzzzzzzz"); </script> 循环之前执行：var sheepCounted = 0; //Start 每次循环之前执行：sheepCounted < 10; //Condition 每次循环之后执行：sheepCounted++ // Increment7. 循环访问数组元素
var animals = ["Lion", "Flamingo", "Polar Bear", "Boa Constrictor"]; for (var i = 0; i < animals.length; i++) { console.log("This zoo contains a " + animals[i] + "."); }8. 循环访问字符串中的字符
<script> var name = "Nick"; for (var i = 0; i < name.length; i++) { console.log("My name contains the letter " + name[i] + "."); } </script>9. 循环数字
for (var x = 2;x < 10000; x = x * 2) { console.log(x); }10. 把for循环改成while循环
var x=2; while(x<10000) { console.log(x); x = x * 2; }