<script type="text/javascript">
function assert(condition, message){
if (!condition){
throw new Error(message);
}
}
function divide(num1, num2){
assert(typeof num1 == "number" && typeof num2 == "number",
"divide(): Both arguments must be numbers.");
return num1 / num2;
}
var result = divide(10, 23);
result = divide("hi", 3);
</script>错误： Error 为全局对象
<body>
<script type="text/javascript">
window.onerror = function(message, url, line){
alert(message);
return false;
};
throw new Error("Something bad happened.");
</script>
</body>通过原型链的继承 - 实现自定义错误
<script type="text/javascript">
function CustomError(message){
this.name = "CustomError";
this.message = message;
}
CustomError.prototype = new Error();
function process(values){
if (!(values instanceof Array)){
throw new CustomError("process(): Argument must be an array.");
}
values.sort();
for (var i=0, len=values.length; i < len; i++){
if (values[i] > 100){
return values[i];
}
}
return -1;
}
process("string");
</script>try{...}catch{...}finally{...} 捕获异常
<script type="text/javascript">
try {
window.someNonexistentFunction();
} catch (error){
alert(error.name);
alert(error.message);
}
</script><body>
<script type="text/javascript">
function testFinally(){
try {
return 2;
} catch (error){
return 1;
} finally {
// 有 finally 之后，返回的值就是 finally 里面的
// 如果 finally 里没 return 调用，则返回上一个 return 的值
return 0;
}
}
function testWithoutFinally(){
try {
return 2;
} catch (error){
return 1;
}
}
alert(testFinally()); // 0
alert(testWithoutFinally()); // 2
</script>
</body>