try...catch

Baseline Widely available

This feature is well established and works across many devices and browser versions. Its been available across browsers since 20157.

try...catch try...catch

try...catch try catch try try catch try try catch try catch finally try catch try...catch

try...catch (1-12) InvalidMonthNo catch monthName unknown

function getMonthName(mo) {
  mo = mo - 1; //  (1=Jan, 12=Dec)
  var months = new Array(
    "Jan",
    "Feb",
    "Mar",
    "Apr",
    "May",
    "Jun",
    "Jul",
    "Aug",
    "Sep",
    "Oct",
    "Nov",
    "Dec",
  );
  if (months[mo] != null) {
    return months[mo];
  } else {
    throw "InvalidMonthNo";
  }
}

try {
  // 
  monthName = getMonthName(myMonth); // 
} catch (e) {
  monthName = "unknown";
  logMyErrors(e); // 
}

catch

catch try catch

catch try...catch catch try

catch

catch (catchID) {
  statements
}

catch catchID throw catch JavaScript catch catch

catch

try {
  throw "myException"; // 
} catch (e) {
  // 
  logMyErrors(e); // 
}

catch try catch catch catch catch

function getCustInfo(name, id, email) {
  var n, i, e;

  if (!validate_name(name)) throw "InvalidNameException";
  else n = name;
  if (!validate_id(id)) throw "InvalidIdException";
  else i = id;
  if (!validate_email(email)) throw "InvalidEmailException";
  else e = email;
  cust = n + " " + i + " " + e;
  return cust;
}

catch

try {
// 
   getCustInfo("Lee", 1234, "lee@netscape.com")
}

catch (e if e == "InvalidNameException") {
// 
   bad_name_handler(e)
}

catch (e if e == "InvalidIdException") {
//  ID 
   bad_id_handler(e)
}

catch (e if e == "InvalidEmailException") {
// 
   bad_email_handler(e)
}

catch (e){
// 
   logError(e)
}

finally

finally try catch try...catch finally catch finally

finally Script Script JavaScript finally Script

openMyFile();
try {
  writeMyFile(theData); // 
} catch (e) {
  handleError(e); // 
} finally {
  closeMyFile(); // 
}

try...catch

try...catch try...catch catch try...catch catch

Error

name message name DOMException Errormessage

catch

function doSomethingErrorProne () {
   if (ourCodeMakesAMistake()) {
      throw (new Error('The message'));
   }
   else {
      doSomethingToGetAJavascriptError();
   }
}
....
try {
   doSomethingErrorProne();
}
catch (e) {
   alert(e.name);//  'Error'
   alert(e.message); //  'The message'  JavaScript 
}

page(Doc) not found /zh-TW/docs/Core_JavaScript_1.5_::throw_

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