| === | 等于(检查值和类型) | x=5 y="5" x==y 返回值为 true x===y 返回值为 false |
try { adddlert("Welcome guest!") //此处正确语法为:alert("..."); }catch(err) { txt="There was an error on this page.\n\n" txt+="Click OK to continue viewing this page,\n" txt+="or Cancel to return to the home page.\n\n" if(!confirm(txt)) //产生确认框; { document.location.href="http://www.w3school.com.cn/" } } } </script> </head> <body> <input type="button" value="View message" οnclick="message()" /> </body> </html> 若要捕获错误描述,代码为:err.description 10.判断变量是否Number型: isNaN(x) 11.如何使用 onerror 事件来捕获错误?
<html> <head> <script type="text/javascript">onerror=handleErr var txt="" function handleErr(msg,url,l) { txt="There was an error on this page.\n\n" txt+="Error: " + msg + "\n" txt+="URL: " + url + "\n" txt+="Line: " + l + "\n\n" txt+="Click OK to continue.\n\n" alert(txt)return true } function message() { adddlert("Welcome guest!") } </script> </head> <body> <input type="button" value="View message" οnclick="message()" /> </body> </html> 12.如何在 JavaScript 中使用反斜杠来向文本字符串添加特殊字符? | 代码 | 输出 |
|---|---|
| \' | 单引号 |
| \" | 双引号 |
| \& | 和号 |
| \\ | 反斜杠 |
| \n | 换行符 |
| \r | 回车符 |
| \t | 制表符 |
| \b | 退格符 |
| \f | 换页符 |
toUpperCase()) </script> 上面的代码输出为: HELLO WORLD! 14.如何为字符串添加样式?<html> <body><script type="text/javascript">var txt="Hello World!"document.write("<p>Big: " + txt.big() + "</p>") document.write("<p>Small: " + txt.small() + "</p>")document.write("<p>Bold: " + txt.bold() + "</p>") document.write("<p>Italic: " + txt.italics() + "</p>")document.write("<p>Blink: " + txt.blink() + " (does not work in IE)</p>") document.write("<p>Fixed: " + txt.fixed() + "</p>") document.write("<p>Strike: " + txt.strike() + "</p>")document.write("<p>Fontcolor: " + txt.fontcolor("Red") + "</p>") document.write("<p>Fontsize: " + txt.fontsize(16) + "</p>")document.write("<p>Lowercase: " + txt.toLowerCase() + "</p>") document.write("<p>Uppercase: " + txt.toUpperCase() + "</p>")document.write("<p>Subscript: " + txt.sub() + "</p>") document.write("<p>Superscript: " + txt.sup() + "</p>")document.write("<p>Link: " + txt.link() + "</p>") </script></body> </html>运行结果为:Big: Hello World!Small: Hello World!Bold: Hello World!Italic: Hello World!Blink: Hello World! (does not work in IE) //文字闪烁 Fixed: Hello World!Strike: Lowercase: hello world!
Uppercase: HELLO WORLD! Subscript: Hello World!Superscript: Hello World!Link: 15.如何使用 indexOf() 来定位字符串中某一个指定的字符首次出现的位置?<html> <body><script type="text/javascript">var str="Hello world!" document.write(str.indexOf("Hello") + "<br />") document.write(str.indexOf("World") + "<br />") document.write(str.indexOf("world"))</script></body> </html>运行结果为:0 -1 6 16.如何使用 match() 来查找字符串中特定的字符，并且如果找到的话，则返回这个字符,否则返回null<html> <body><script type="text/javascript">var str="Hello world!" document.write(str.match("world") + "<br />") document.write(str.match("World") + "<br />") document.write(str.match("worlld") + "<br />") document.write(str.match("world!"))</script></body> </html>运行结果为:world null null world! 17.如何使用 replace() 方法在字符串中用某些字符替换另一些字符<html> <body><script type="text/javascript">var str="Visit Microsoft!" document.write(str.replace(/Microsoft/,"W3Schools")) //此处用的'/'可以用双引号替代</script> </body> </html>18.如何获得当日的日期和时间?<html> <body><script type="text/javascript">document.write(Date())</script></body> </html> 运行结果为:Wed Feb 27 09:26:53 2008 19.如何使用 setFullYear() 得到精确的日期?<html> <body><script type="text/javascript">var d = new Date() d.setFullYear(1992,10,3) document.write(d)</script></body> </html> 运行结果为:Tue Nov 3 09:48:00 UTC+0800 1992 此处改变setFullYear(1992,10,3)中的参数,即可查询设定参数的精确日期 20.toUTCString():返回一个已被转换为字符串的，用全球标准时间 (UTC)表示的日期.<html> <body><script type="text/javascript">var d = new Date() document.write (d.toUTCString())</script></body> </html> 运行结果为:Wed, 27 Feb 2008 01:54:59 UTC //我们与全球标准时间相差8个时区UTC+0800即为我们的北京时间