Js练习
显示和隐藏，改变display属性(点击查看图片)
关键代码：
e.style.display = "block";
e.style.display = "none";源码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>显示和隐藏</title>
<script type="text/javascript">
function showPicture(){
//普通方式获得控件实例
var e = document.getElementById("myimg");
e.style.display = "block";
}
function hidePicture(){
//querySelector是html5增加的
//id前面得写#,class前面得写
document.querySelector("#myimg").style.display = "none";
//标签直接写即可,获取到第一个img标签
//document.querySelector("img").style.display = "none";
}
</script>
</head>
<body>
<a href="javascript:void(0);"onclick="showPicture()">查看图片</a>
<a href="javascript:void(0);"onclick="hidePicture()">隐藏图片</a>
<br />
<img id="myimg" src="http://www.w3school.com.cn/i/eg_mouse.jpg" style="display: none;" >
</body>
</html>
鼠标滑动更改内容 onmouseover
关键：
onmouse事件
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript">
function moveToBlue(){
var e = document.querySelector("#btn_blue");
var e2 = document.querySelector("#btn_green");
var div = document.querySelector("#content");
e.style.border = "1px solid #ccc";
e.style.backgroundColor = "white";
e2.style.border = "none";
e2.style.backgroundColor = "none";
div.style.backgroundColor = "blue";
}
function moveToGreen(){
var e = document.querySelector("#btn_blue");
var e2 = document.querySelector("#btn_green");
var div = document.querySelector("#content");
e2.style.border = "1px solid #ccc";
e2.style.backgroundColor = "white";
e.style.border = "none";
e.style.backgroundColor = "none";
div.style.backgroundColor = "green";
}
</script>
</head>
<body>
<div style="width: 100px;height: 50px;">
<button id="btn_blue" style="width: 45px;"onmousemove="moveToBlue()">蓝色</button>
<button id="btn_green" style="width: 45px;"onmousemove="moveToGreen()">绿色</button>
<div id="content" style="background-color: blue;width: auto;height: 50px;"></div>
</div>
<br />
<img id="myimg" src="http://www.w3school.com.cn/i/eg_mouse.jpg" style="display: none;">
</body>
</html>
时间自动更新
关键代码：
Js中内置了Date对象
- getFullYear 年
- getMonth 月
- getDate 日
- getHours 小时
- getMinutes 分钟
- getSeconds 秒
- getDay 星期几（0-6） 星期日为0
var now = new Date();
var time =now.getFullYear() + '年' + now.getMonth() + '月'
+ now.getDate() + '日'
+now.getHours() +'时' + now.getMinutes() +'分' + now.getSeconds() + '秒';- setTomeout(fn, 周期：豪秒): 周期只会执行一次
- setInterval(fn, 周期：豪秒)： 间隔周期一直执行
源码：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title>时间自动更新</title>
</head>
<body>
<p></p>
<script type="text/javascript">
function setTime() {
var date = new Date();
var time = date.toTimeString();
document.querySelector("p").innerText = time;
}
setTime();
//setIime不能加上括号
// setInterval(setTime, 1000);
//加括号得得在外层加双引号或者单引号
setInterval("setTime()", 1000);
</script>
</body>
</html>源码（es拼接字符串）：
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
</head>
<body>
<p></p>
<script type="text/javascript">
function setTime() {
var now = new Date();
// 通过css的选择符获得html元素
var timer1 = document.querySelector('p');
var year = now.getFullYear();
var month = now.getMonth() + 1;
var date = now.getDate();
var hours = now.getHours();
var minutes = now.getMinutes();
var seconds = now.getSeconds();
//es6中模板字符串,拼接
timer1.innerText = `${year}年${month}月${date}日${hours}时${minutes}分${seconds}秒`;
}
setTime();
//setIime不能加上括号
// setInterval(setTime, 1000);
//加括号得得在外层加双引号或者单引号
setInterval("setTime()", 1000);
</script>
</body>
</html>
表单
关键代码：e.checked=true;
全选和反选的实现
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<title></title>
<script type="text/javascript">
function selectAll() {
var hobbys = document.getElementsByName("hobby");
var btn = document.getElementById("checkall");
//原生for,推荐使用这一种
/*
for (var i = 0; i < hobbys.length; i++) {
if (btn.checked) {
hobbys[i].checked = true;
} else {
hobbys[i].checked = false;
}
}
*/
//使用foreach,使用HBuilderX,在内置的浏览器会报错,提示foreach不起作用
//使用谷歌浏览器打开则没有问题,下面使用lambda也是如此情况,可能是HBuilder的bug
hobbys.forEach(function(hobby) {
//如果全选的是选中,则把全部设置为选中的状态,否则设置为未选中
if (btn.checked) {
hobby.checked = true;
} else {
hobby.checked = false;
}
});
//使用lambda
/*
hobbys.forEach((hobby) => {
console.log(hobby);
if (btn.checked) {
hobby.checked = true;
} else {
hobby.checked = false;
}
});
*/
}
function selectRevese() {
var hobbys = document.getElementsByName("hobby");
for (var i = 0; i < hobbys.length; i++) {
//设置为另外的状态
hobbys[i].checked = !hobbys[i].checked;
}
}
</script>
</head>
<body>
<input type="checkbox" name="hobby">读书<br><br>
<input type="checkbox" name="hobby">电影<br><br>
<input type="checkbox" name="hobby">游戏<br><br>
<input type="checkbox" name="hobby">游泳<br><br>
<input type="checkbox" name="hobby">写代码<br><br>
<input type="checkbox" id="checkall" onclick="selectAll()">全选 </input>
<button type="button" onclick="selectRevese()">反选</button>
</body>
</html>