问在HTML5/javascript中创建异常处理程序

EN

function five_is_bad(x) {
    if (x===5) {
        // `x` should never be 5! Throw an error!
        throw new RangeError('Input was 5!');
    }
    return x;
}

console.log('a');
try {
    console.log('b');
    five_is_bad(5); // error thrown in this function so this 
                    // line causes entry into catch
    console.log('c'); // this line doesn't execute if exception in `five_is_bad`
} catch (ex) {
    // this only happens if there was an exception in the `try`
    console.log('in catch with', ex, '[' + ex.message + ']');
} finally {
    // this happens either way
    console.log('d');
}
console.log('e');
/*
a
b
in catch with RangeError {} [Input was 5!]
d
e
*/

function exceptionhandler() {
    try {
        if (x===5) {
            // do something  
        }
    } catch(ex) {
        throw new Error("Boo! " + ex.message)
    }
}