本例检测输入变量的值。如果值是错误的，会抛出一个异常（错误）。catch 会捕捉到这个错误，并显示一段自定义的错误消息：
<script>function myFunction(){try ?{ ?var x=document.getElementById("demo").value; ?if(x=="") ???throw "empty"; ?if(isNaN(x)) throw "not a number"; ?if(x>10) ????throw "too high"; ?if(x<5) ?????throw "too low"; ?}catch(err) ?{ ?var y=document.getElementById("mess"); ?y.innerHTML="Error: " + err + "."; ?}}</script><h1>My First JavaScript</h1><p>Please input a number between 5 and 10:</p><input id="demo" type="text"><button type="button" onclick="myFunction()">Test Input</button><p id="mess"></p>参考：JavaScript 错误 - Throw、Try 和 Catch
JS——try catch throw
原文地址：http://www.cnblogs.com/wuqiuxue/p/7685829.html