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JavaScript quick start case tutorial
- 巴扎黑Original
- 2017-08-09 14:07:411978browse
JavaScript Quick Start
1. js generates text
<!--
js一般是写在head标签里面
-->
<script>
document.write("我是天才！！");
document.write("我是废才!!");
</script>
2. js generates tags
<script>
document.write("我是天才<br/>");
document.write("我是废才<hr/>");
document.write("我是鬼才 ");
document.write("我是人才");
</script>
3. js writing position and execution order
<!--
1，书写位置：js是一种弱类型的语言，所以语法不是特别的严格，但是一般js代码是写在head标签里面
2， 执行顺序：js的解释执行是从上往下进行的。
-->
<script>
alert("哈哈");
alert("哼哼");
alert("嘎嘎");
</script>
4. Import external js files
<!--
使用src属性导入外部的js文件
引入js文件需要占用一个script标签，执行代码时需要另取一个script标签
-->
<script src="../js/mylove.js"></script>
<script>
var sum = getSum(2, 3);
alert(sum);
alert("我是来自于内部的js");
</script>
mylove.js:
alert("我是来自于外部的js文件代码");
function getSum(a,b){
return a + b;
}
5. Variable declaration in js
<script> // 由于javascript是一种弱类型语言，所以定义变量都是使用一个关键字var // 定义一个数字类型 var number = 10; // 定义一个字符串 var str = "aaabbb"; // 定义一个数组 var arr = [1,2,3,"haha","yue"]; </script>
6. Judgment statement in js if
<script>
// 输入1-10之间的数字，如果大了则提示输入过大，如果小了则提示输入小了，在1-10之间则把输入的数字打印出来！
var number= prompt("输入一个1-10之间的数字");
if(number > 10){
alert("你输入的数字大了！");
}else if(number < 1){
alert("你输入的数字小了！");
}else{
alert("你输入的数字为：" + number);
}
</script>
7. Three kinds of message boxes in js
<script>
// 1 警告框
alert("我是天才");
// 2 确认框,返回值为true则表示确认，false表示取消
var result = confirm("欲练此功必须自宫，你还练吗？");
if(result){
alert("自宫成功！");
}else{
alert("怂了吧!~?");
}
// 3 提示框输入框
var name = prompt("请输入名字","王八");
if(name!=""&& name!=null){
alert("您输入的名字为：" + name);
}
</script>
8. Functions in js
<script>
// 求和函数
function getSum(a, b) {
return a + b;
}
var sum = getSum(3, 6);
alert("和为：" + sum);
// 定义重载函数
function add(){
alert("我是无参函数！");
}
function add(i,j){
alert("我是有参函数!");
var sum = i + j;
alert("有参函数和为：" + sum);
}
add();
// 调用无参的函数时，结果却是弹出有参的提示
// 这是因为js中的函数不能重载，只可以有一个同名函数，多了的会被最后的一个覆盖掉
add(2,4); // 正常输出
add(2,4,6); // 输出和仍为6，因为函数只有两个参数，多传入的值是无效的
</script>
9. Two kinds of for loops in js
<script>
// 使用for循环求1-100的和
var sum = 0;
for (var i = 1; i <= 100; i++) {
sum += i;
}
alert("1-100的和是：" + sum);
// 使用for循环打印九九乘法表
for (var i = 1; i <= 9; i++) {
for (var j = 1; j <= i; j++) {
document.write(j + "*" + i + "=" + j * i + " ");
}
document.write("<br/>");
}
// for循环打印标题
for(var i = 1; i <=7;i ++){
document.write("<h"+i+">" +"我是"+ i + "级标题"+"<h"+i+">");
}
// for循环遍历月份
document.write("<br>"+"<select>");
for(var i = 1; i <=12;i ++){
document.write("<option>");
document.write(i);
document.write("</option>");
}
document.write("</select>");
// 高级for,x是角标
var str = ["haha","hdhd",99,10,'ooo'];
for(x in str){
alert(str[x]);
}
</script>
10. Exception handling in js try{}catch(){}
<script>
/**
* js中处理异常有两种方式，第一种是用try{} catch(){}语句块处理
* 还有就是你认为代码会出错时用throw关键字把错误跑出去，然后用catch里进行捕获
*/
var count = 3 * 8;
haha 让你输出不了;
alert(count);
function add(a, b) {
try {
hahahaha
return a + b;
} catch (err) {
alert("出错了吧");
}
}
add(1,4);
function value(){
var sum = prompt("输入1-100的数字：");
if(sum == "" || sum==null){
alert("输入为空啊");
return;
}
try{
if(sum > 100){
throw "e1";
}else if( sum < 1){
throw "e2";
}else{
alert("你输入的数字是：" + sum);
}
}catch(e){
if(e == "e1"){
alert("输入过大了");
}else if(e == "e2"){
alert("输入过小了");
}
}
}
value();
</script>
11. Window object in js
<script>
/**
* window对面表示打开的浏览器对象，主要包括了五个子对象
* 1. Navigator 导航器对象
* 2. History 浏览器历史纪录
* 3. Screen 屏幕
* 4. Document 文档
* 5. Location 位置
*/
</script>
<script>
function me_Navigator(){
document.write(navigator.appCodeName + "<br/>");
document.write(navigator.appVersion + "<br/>");
document.write(navigator.appName + "<br/>");
document.write(navigator.geolocation + "<br/>");
}
me_Navigator();
// 上一步
function clickme(){
history.back();
}
// 跳转
function tiancai(){
var result = confirm("要去百度官网吗？");
if(result){
location.href="index.html";
}
}
</script>
12. Timer
<html>
<head>
<meta charset="utf-8">
<title></title>
<script>
// 电子显示时钟
function showTime(){
var date = new Date();
var canvas = document.getElementById("showcanvas");
var hours = date.getHours();
var min = date.getMinutes();
var sec = date.getSeconds();
canvas.innerHTML = "<h3>" + hours + ":" + min + ":" + sec + "</h3>";
}
setInterval("showTime()",1000);
// 倒计时显示器
var i = 0;
var t = 0;
function backTime(){
var date = new Date();
var canvas = document.getElementById("showcanvas");
var hours = date.getHours();
var min = date.getMinutes();
var sec = date.getSeconds();
canvas.innerHTML = "<h3>" + hours + ":" + min + ":" + sec + "</h3>";
i ++ ;
if(i == 5){
clearInterval(t);
}
}
t = setInterval("backTime()",1000);
</script>
</head>
<body onload="backTime()">
<div id="showcanvas"></div>
</body>
</html>
13. Draw a duck
The picture materials are as follows
-
The code is as follows
<script> var i = 0; var t; function image(){ document.getElementById("img").src="../img/"+ i +".png"; i ++; if(i == 7){ clearInterval(t); alert("画完了，好玩吧！"); } } t = setInterval("image()",1000); </script> </head> <body onload="image()"> <img id="img"/> </body>
14. String Object
<script>
var str = "我就是天才啊，无人能挡，哈哈哈哈";
document.write("我的长度是:" + str.length + "<br/>");
document.write(str + "<br/>");
document.write(str.big() + "<br/>");
document.write(str.blink() + "<br/>");
document.write(str.bold() + "<br/>")
var str1 = "LSDVASLEOSVN";
document.write(str1.toLocaleLowerCase() + "<br/>");
var str2 = "sldvjlwelvdnlsh";
document.write(str2.toLocaleUpperCase());
</script>
15. Time and array
<script>
// 时间
var date = new Date();
document.write(date.getFullYear() + "年");
document.write(date.getMonth() + 1 + "月");
document.write(date.getDate() + "日   ");
document.write(date.getHours() + "时");
document.write(date.getMinutes() + "分");
document.write(date.getSeconds() + "秒<br>");
</script>
<script>
// 数组
var arr = [2,4,78,34,"haha"];
for(x in arr){
alert(arr[x]);
}
alert("数组最开始的长度：" + arr.length);//5
// 给第10个值赋值
arr[10] = 0;
alert("数组赋值后的长度：" + arr.length);//11
// 数组排序
arr1 = [1,7,6,3,9,2,4,8,5];
// 自定义排序方式
function byNumber(a,b){
return a-b;
}
document.write(arr1 + "<br>")
document.write(arr1.sort(byNumber)+ "<br>");
// 冒泡排序法
arr3 = [1,7,6,3,9,2,4,8,5];
for(var i = 0; i < arr3.length-1;i++){
for(var j = i+1;j < arr3.length;j++){
if(arr3[i] > arr3[j]){
var temp = arr3[i];
arr3[i] = arr3[j];
arr3[j] = temp;
}
}
}
document.write("冒泡排序后的结果：" + "<br>")
document.write(arr1 + "<br>")
</script>
16. Getting started with dom
<html>
<head>
<meta charset="utf-8">
<title></title>
<script>
function init(){
document.getElementById("name").value="请输入你的名字";
}
function _focus(){
document.getElementById("name").value="";
}
function _blur(){
var value = document.getElementById("name").value;
if(value == "" || value==null){
document.getElementById("name").value="请输入你的名字";
}else{
document.getElementById("name").style.color="aqua";
}
}
</script>
</head>
<body onload="init()">
<!--
onfocus:聚焦
onblur:失去焦点
-->
<input type="text" id="name" onfocus="_focus()" onblur="_blur()"/>
</body>
</html>
17. How to get html tags
<html>
<head>
<meta charset="utf-8">
<title></title>
<script>
function init(){
// 获取id
document.getElementById("text").value="我是天才";
// 获取name
document.getElementsByName("name")[1].value = "20岁";
// 获取标签
document.getElementsByTagName("input")[2].value="男";
}
</script>
</head>
<body onload="init()">
输入姓名：<input type="text" name="name" id="text"/><br>
输入年龄：<input type="text" name="name" id="text"/><br>
输入性别：<input type="text" name="name" id="text"/>
</body>
</html>
18. The elegance of Jquery Jianghu
The rendering is as follows
The data file is as follows
- ##juery The class library can be downloaded from the Internet. The data.txt data is as follows: [
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food1.jpg",
"desc":"九毛九"
},
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food2.jpg",
"desc":"Real Kung Fu"
},
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food3.jpg",
"desc":"哥乐"
},
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food4.jpg",
"desc":"Pizza Hut"
},
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food5.jpg",
“desc”:”KFC”
},
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food6.jpg",
"desc":"King Yonghe"
},
{"picpath":"http://127.0.0.1:8020/Day03_javascript_%E4%BD%9C%E4%B8%9A/img/food/food7.jpg",
"desc":"Hongli Village"
}
] - The picture material is as follows
- ##The code is as follows
-
<head> <meta charset="utf-8"> <title></title> <!-- 引入jquery类库文件 --> <script type="text/javascript" src="../js/jquery-1.8.3.min.js"></script> <script> // 发送一个请求给服务器，把服务器上的数据拿到 $.get(".../data.txt",function(data){ var jsonArr = eval(data); for(x in jsonArr){ var picpath = jsonArr[x].picpath; var desc = jsonArr[x].desc; // 创建图片节点 var imgNode = document.createElement("img"); imgNode.src = picpath; imgNode.setAttribute("class","img_style"); // 创建p节点 var pNode = document.createElement("p"); pNode.innerHTML = desc; pNode.style.color = "red"; pNode.align = "center"; // 创建一个div节点 var divNode = document.createElement("div"); divNode.setAttribute("class","div_style"); divNode.appendChild(imgNode); divNode.appendChild(pNode); document.getElementById("container").appendChild(divNode); } }); </script> <style> .div_style{ position: relative; float: left; margin: 20px; } .img_style{ width: 150px; height: 150px; } </style> </head> <body> <div id="container"></div> <p align="center"></p> </body>
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