html 基础之canvas 和 localStorage

1，建立一个canvas 画布：

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8     <style>
 9         body {
10             background: #f00;
11         }
12         #canvas {
13             background: #000;
14         }
15     </style>
16 </head>
17 <body>
18     <canvas id="canvas" width="300" height="200"></canvas>
19 </body>
20 </html>

1.2 动态创建canvas ：

 1  <style>
 2         #canvas {
 3             border: 1px solid blue;
 4         }
 5     </style>
 6     <script>
 7         window.onload = function() {
 8             var Ocanvas = document.createElement('canvas');
 9             // Ocanvas.style.width = "300";
10             // Ocanvas.style.height = "200";
11             // Ocanvas.style.background = "red";
12             Ocanvas.id = "canvas";
13             Ocanvas.width = "300";
14             Ocanvas.height = "200";
15             Ocanvas.style.background = "red";
16             document.body.appendChild(Ocanvas);
17         }
18  </script>

1.3 使用canvas :画直线

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8     <style>
 9         #canvas {
10             border: 1px solid blue;
11             background: white;
12         }
13         
14         body {
15             background: black;
16         }
17     </style>
18     <script>
19         window.onload = function() {
20             var Ocanvas = document.getElementById("canvas");
21             var Og = Ocanvas.getContext('2d'); // 获取2d 绘图环境
22             Og.lineWidth = 10; // 线条宽度
23             Og.strokeStyle = "#1133fb"; // 线条样式
24             Og.moveTo(100, 100); //起始点
25             Og.lineTo(200, 200); //结束点
26             Og.stroke(); // 渲染
27         }
28     </script>
29 </head>
30 <body>
31     <canvas id="canvas" width="500" height="250"></canvas>
32 </body>
33 </html>

1.4 canvas 作画：画圆弧

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8     <style>
 9         #canvas {
10             border: 1px solid blue;
11             background: white;
12         }
13         body {
14             background: black;
15         }
16     </style>
17     <script>
18         window.onload = function() {
19             var Ocanvas = document.getElementById("canvas");
20             var Og = Ocanvas.getContext('2d'); // 获取2d 绘图环境
21             //beginPath() 方法开始一条路径，或重置当前的路径。
22             Og.beginPath();
23             Og.lineWidth = 10;
24             Og.strokeStyle = "#aa0072";
25             // 画圆，第一个参数为圆心的x,第二个参数为圆心的y,第三个参数为圆的半径，第四个参数为圆的起始点，第五个参数为圆的结束点，第六个参数为画圆的方向（false为顺时针，true为逆时针）
26             Og.arc(150, 100, 70, 0, 2 * Math.PI / 4, false);
27             Og.stroke(); // 渲染
28         }
29     </script>
30 </head>
31 <body>
32     <canvas id="canvas" width="500" height="250"></canvas>
33 </body>
34 </html>

运行结果：

2.1 sessionStorage 基础：浏览器上的临时变量，只要不关闭，临时变量就一直存在，直到关闭浏览器。临时变量的设置：window.sessionStorage.setItem('name','值'); 获取临时变量：window.session.getItem('name')

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8     <style>
 9     </style>
10     <script>
11         window.onload = function() {
12             var abtn = document.querySelectorAll("input");
13             var obj = {
14                 name: "huanying2015",
15                 sex: "man",
16                 age: 25
17             }
18             abtn[0].onclick = function() {
19                 // sessionStorage  存储在浏览器上的临时变量，只要不关闭浏览器，就一直存在，只要一关比浏览器，就不存在了
20                 window.sessionStorage.setItem('name', obj['name']);
21             }
22             abtn[1].onclick = function() {
23                 alert(window.sessionStorage.getItem('name'));
24             }
25             abtn[2].onclick = function() {
26                 // 清除浏览器上的临时变量
27                 window.sessionStorage.removeItem("name");
28             }
29         }
30     </script>
31 </head>
32 <body>
33     <input type="button" value="设置">
34     <input type="button" value="获取">
35     <input type="button" value="删除">
36 </body>
37 </html>

运行结果：

2.2 localStorage :永久性存储，与sessionStorage不同的是，关闭浏览器，变量的值也不会消失

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8     <script>
 9         window.onload = function() {
10             var aInput = document.querySelectorAll("input");
11             var obj = {
12                 name: 'huanying2015',
13                 sex: 'man',
14                 age: 25
15             }
16             aInput[0].onclick = function() {
17                 window.localStorage.setItem('name', obj['name']);
18                 window.localStorage.setItem('sex', obj['sex']);
19                 window.localStorage.setItem('age', obj['age']);
20             }
21             aInput[1].onclick = function() {
22                 alert(window.localStorage.getItem('name') + '------' + window.localStorage.getItem('sex') + '-------' + window.localStorage.getItem('age'));
23             }
24             aInput[2].onclick = function() {
25                 window.localStorage.removeItem('name');
26                 window.localStorage.removeItem('sex');
27                 window.localStorage.removeItem('age');
28             }
29         }
30     </script>
31 </head>
32 <body>
33     <input type="button" value="设置" />
34     <input type="button" value="获取" />
35     <input type="button" value="删除" />
36 </body>
37 </html>

运行结果：关闭浏览器之后，之前设置的变量还在，还可以直接通过window.localStorage.getItem('属性名') 来直接获取

3. localStorage 的应用：在网页中输入变量名称，关闭网页时，变量名称存储的值还在，当再次打开网页时，浏览器直接调用 localStorage 中的值

 1 <!DOCTYPE html>
 2 <html lang="en">
 3 <head>
 4     <meta charset="UTF-8">
 5     <meta name="viewport" content="width=device-width, initial-scale=1.0">
 6     <meta http-equiv="X-UA-Compatible" content="ie=edge">
 7     <title>Document</title>
 8     <style>
 9     </style>
10     <script>
11         window.onload = function() {
12             var aInput = document.querySelectorAll("input");
13             var Otxt = document.querySelector("textarea");
14             if (window.localStorage.getItem('userName123')) {
15                 aInput[0].value = window.localStorage.getItem('userName123');
16             }
17             for (var i = 0, len = aInput.length; i < len; i++) {
18                 if (window.localStorage.getItem('sex1') == aInput[i].value) {
19                     aInput[i].checked = true;
20                 }
21             }
22             if (window.localStorage.getItem('shuoming')) {
23                 Otxt.value = window.localStorage.getItem('note');
24             }
25 
26             window.onunload = function() {
27                 if (aInput[0].value) {
28                     window.localStorage.setItem('userName123', aInput[0].value);
29                 }
30                 for (var i = 0, len = aInput.length; i < len; i++) {
31                     if (aInput[i].checked == true) {
32                         window.localStorage.setItem('sex1', aInput[i].value);
33                     }
34                 }
35                 if (Otxt.value) {
36                     window.localStorage.setItem('shuoming', Otxt.value);
37                 }
38             }
39         }
40     </script>
41 </head>
42 <body>
43     <p>
44         用户名：<input type="text">
45     </p>
46     <br>
47     <p>
48         性别：<br>
49         <input type="radio" name="sex1" value="男"> 男
50         <input type="radio" name="sex1" value="女"> 女
51     </p>
52     <p>
53         备注：
54         <textarea name="" id="" cols="30" rows="10"></textarea>
55     </p>
56 </body>
57 </html>

运行结果：

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原文地址：https://www.cnblogs.com/huanying2015/p/8592092.html