Javascript条件语句之if else

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>hello world</title>
 6     </head>
 7     <body>
 8         <p>如果时间小于10：00，则生成问候“good morning，如果时间大于10：00小于20：00，则生成问候“good day”，否则生成问候“goodevening”</p>
 9         <button onclick="myFunction()">点击这里</button>
10         <p id="demo"></p>
11         <script>
12             function myFunction(){
13                 var x='';
14                 var time= new Date().getHours();
15                 if (time<10){
16                     x ="good morning!"
17                 }
18                 else if(10<time<20){
19                     x ="good day"
20 
21                 }
22                 else{
23                     x ="good evening"
24                 }
25                 document.getElementById("demo").innerHTML=x
26             }
27             
28         </script>
29     </body>
30 </html>

 Javascript之switch

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript Switch</title>
 6     </head>
 7     <body>
 8         <p>click this button to get witch day today</p>
 9         <button onclick="myFunction()">click it</button>
10         <p id="demo"></p>
11         <script>
12             function myFunction(){
13                 var x;
14                 var d = new Date().getDay();
15                 console.log(d)
16                 switch (d){
17                     case 0:x="今天是星期日";
18                     break;
19                     case 1:x="今天是星期一";
20                     break;
21                     case 2:x="今天是星期二";
22                     break;
23                     case 3:x="今天是星期三";
24                     break;
25                     case 4:x="今天是星期四";
26                     break;
27                     case 5:x="今天是星期五";
28                     break;
29                     case 6:x="今天是星期六";
30                     break;
31                 }
32             document.getElementById("demo").innerHTML=x
33             }
34            
35         </script>
36     </body>
37 </html>

Javascript之for循环

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript for 循环</title>
 6     </head>
 7     <body>
 8         <p>cars is </p>
 9         <script>
10             var cars = ["bms","volovo","byd","benz", "..."]
11             for (var i=0; i<cars.length; i++){
12                 document.write(cars[i], +'<br>')
13                 console.log(cars[i])
14             }
15         </script>
16     </body>
17 </html>
 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript for 循环啊</title>
 6     </head>
 7     <body>        
 8         <button onclick="myFunction()">click here to calculate it </button>
 9         <p id="demo"></p>
10         <script>
11             function myFunction(){
12                 var x ="";
13                 for (var i=0; i<5; i++){
14                     x = x + "number is "+ i + "<br>"
15                     
16                 }
17             document.getElementById("demo").innerHTML=x
18         }
19             
20         </script>
21     </body>
22 </html>

Javascript之for…in循环

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="uff-8">
 5         <title>JavaScript for/in 循环</title>
 6     </head>
 7     <body>
 8         <script>
 9         var person={
10             fname:"Bill",
11             lname:"Gates",
12             age:56,
13             hobby:"sport"
14         }
15         for (x in person){
16             txt = person[x]
17             console.log(txt)
18         }
19         
20     </script>
21     </body>
22 </html>

Javascript之while循环

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript while 循环啊</title>
 6     </head>
 7     <body>
 8         <p>JavaScript while 循环啊</p>
 9         <p>
10             while (条件){
11                 需要执行的代码块
12             }
13         </p>
14         <p>当i<10，打印所有值</p>
15         <button onclick="myFunction()">click here</button>
16         <p id="demo"></p>
17         <script>
18             function myFunction(){
19                 var x='', i=0;
20                 while (i<10){
21                     x = x +"this number is " + i + "<br>";
22                     i++
23                 }
24             document.getElementById("demo").innerHTML=x
25             }
26         </script>
27         
28     </body>
29 </html>

JavaScript之do…while循环

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript do while</title>
 6     </head>
 7     <body>
 8         <p>
 9             语法:do/while 循环是 while 循环的变体。该循环会在检查条件是否为真之前执行一次代码块，然后如果条件为真的话，就会重复这个循环。
10             do {
11                 需要执行的代码块
12             }
13             while(条件);
14         </p>
15         <p>点击下面按钮，只要i小于5就一直循环代码</p>
16         <button onclick="myFunction()">点击这里</button>
17         <p id="demo"></p>
18         <script>
19             function myFunction(){
20                 var x="", i=0
21                 do {
22                     x = x + "该数字为"+ i +"<br>";
23                     i++
24                 }
25                 while (i<5)
26                 document.getElementById("demo").innerHTML=x
27             }
28         </script>
29     </body>
30 </html>

 JavaScript之for循环遍历数组

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript for 循环遍历数组值</title>
 6     </head>
 7     <body>
 8         <p>for 循环打印数组所有值啊</p>
 9         <button onclick="myFunction()">点击这里打印所有值</button>
10         <p id="demo"></p>
11         <script>
12             function myFunction(){
13                 //定义一个数组
14                 cars=["BMW","Volvo","Saab","Ford"];
15                 //定义一个自增变量i=0
16                 var i=0
17                 for (;cars[i];){
18                     document.write(cars[i]+"<br>");
19                     i++
20                 }
21             }
22         </script>
23     </body>
24 </html>

JavaScript条件语句之while循环遍历数组

 1 <!DOCTYPE html>
 2 <html>
 3     <head>
 4         <meta charset="utf-8">
 5         <title>JavaScript while 循环遍历数组值</title>
 6     </head>
 7     <body>
 8         <p>while 循环遍历数组值啊</p>
 9         <button onclick="myFunction()">点击这里遍历所有值</button>
10         <p id="demo"></p>
11         <script>
12             function myFunction(){
13                 //定义两个变量
14                 var cars=["BMW","Volvo","Saab","Ford"];
15                 i=0;
16                 while (cars[i]){
17                     document.write(cars[i]+"<br>");
18                     i++
19                 }
20 
21             }
22         </script>
23     </body>
24 </html>

 

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