Javascript----常用小技巧
一.js的各种消息框
（以下代码来自w3school）
1.警告框
alert(
"
消息内容
"
)
2.确认框
代码
<
html
>
<
head
>
<
script type
=
"
text/javascript
"
>
function
disp_confirm()
{
var
r
=
confirm(
"
按下按钮
"
)
if
(r
==
true
)
{
document.write(
"
您按了确认！
"
)
}
else
{
document.write(
"
您按了取消！
"
)
}
}
<
/
script>
<
/
head>
<
body
>
<
input type
=
"
button
"
onclick
=
"
disp_confirm()
"
value
=
"
显示确认框
"
/
>
<
/
body>
<
/
html>
3.提示框
代码
<
html
>
<
head
>
<
script type
=
"
text/javascript
"
>
function
disp_prompt()
{
var
name
=
prompt(
"
请输入您的名字
"
,
"
Bill Gates
"
)
if
(name
!=
null
&&
name
!=
""
)
{
document.write(
"
你好！
"
+
name
+
"
今天过得怎么样？
"
)
}
}
<
/
script>
<
/
head>
<
body
>
<
input type
=
"
button
"
onclick
=
"
disp_prompt()
"
value
=
"
显示提示框
"
/
>
<
/
body>
<
/
html>
二.事件
FF: Firefox, N: Netscape, IE: Internet Explorer
| 属性 | 当以下情况发生时，出现此事件 | FF | N | IE |
|---|---|---|---|---|
| onabort | 图像加载被中断 | 1 | 3 | 4 |
| onblur | 元素失去焦点 | 1 | 2 | 3 |
| onchange | 用户改变域的内容 | 1 | 2 | 3 |
| onclick | 鼠标点击某个对象 | 1 | 2 | 3 |
| ondblclick | 鼠标双击某个对象 | 1 | 4 | 4 |
| onerror | 当加载文档或图像时发生某个错误 | 1 | 3 | 4 |
| onfocus | 元素获得焦点 | 1 | 2 | 3 |
| onkeydown | 某个键盘的键被按下 | 1 | 4 | 3 |
| onkeypress | 某个键盘的键被按下或按住 | 1 | 4 | 3 |
| onkeyup | 某个键盘的键被松开 | 1 | 4 | 3 |
| onload | 某个页面或图像被完成加载 | 1 | 2 | 3 |
| onmousedown | 某个鼠标按键被按下 | 1 | 4 | 4 |
| onmousemove | 鼠标被移动 | 1 | 6 | 3 |
| onmouseout | 鼠标从某元素移开 | 1 | 4 | 4 |
| onmouseover | 鼠标被移到某元素之上 | 1 | 2 | 3 |
| onmouseup | 某个鼠标按键被松开 | 1 | 4 | 4 |
| onreset | 重置按钮被点击 | 1 | 3 | 4 |
| onresize | 窗口或框架被调整尺寸 | 1 | 4 | 4 |
| onselect | 文本被选定 | 1 | 2 | 3 |
| onsubmit | 提交按钮被点击 | 1 | 2 | 3 |
| onunload | 用户退出页面 | 1 | 2 | 3 |
三.try...catch异常处理
代码
<
html
>
<
head
>
<
script type
=
"
text/javascript
"
>
var
txt
=
""
function
message()
{
try
{
adddlert(
"
Welcome guest!
"
)
}
catch
(err)
{
txt
=
"
本页中存在错误。\n\n
"
txt
+=
"
点击“确定”继续查看本页，\n
"
txt
+=
"
点击“取消”返回首页。\n\n
"
if
(
!
confirm(txt))
{
document.location.href
=
"
/index.html
"
}
}
}
<
/
script>
<
/
head>
<
body
>
<
input type
=
"
button
"
value
=
"
查看消息
"
onclick
=
"
message()
"
/
>
<
/
body>
<
/
html>
throw的异常抛出，可以是字符串、整数、逻辑值或者对象
代码
<
html
>
<
body
>
<
script type
=
"
text/javascript
"
>
var
x
=
prompt(
"
请输入 0 至 10 之间的数：
"
,
""
)
try
{
if
(x
>
10
)
throw
"
Err1
"
else
if
(x
<
0
)
throw
"
Err2
"
else
if
(isNaN(x))
throw
"
Err3
"
}
catch
(er)
{
if
(er
==
"
Err1
"
)
alert(
"
错误！该值太大！
"
)
if
(er
==
"
Err2
"
)
alert(
"
错误！该值太小！
"
)
if
(er
==
"
Err3
"
)
alert(
"
错误！该值不是数字！
"
)
}
<
/
script>
<
/
body>
<
/
html>
四.异常捕捉onerror
代码
<
html
>
<
head
>
<
script type
=
"
text/javascript
"
>
onerror
=
handleErr
var
txt
=
""
function
handleErr(msg,url,l)
{
txt
=
"
本页中存在错误。\n\n
"
txt
+=
"
错误：
"
+
msg
+
"
\n
"
txt
+=
"
URL:
"
+
url
+
"
\n
"
txt
+=
"
行：
"
+
l
+
"
\n\n
"
txt
+=
"
点击“确定”继续。\n\n
"
alert(txt)
return
true
}
function
message()
{
adddlert(
"
Welcome guest!
"
)
}
<
/
script>
<
/
head>
<
body
>
<
input type
=
"
button
"
value
=
"
查看消息
"
onclick
=
"
message()
"
/
>
<
/
body>
<
/
html>