Learning JavaScript

Exceptions

Syntax for catch statement

          try {
            ... 
          }
          catch {
            ... 
          }
                
          //example:
          const calcPayments = (numPayments, rate, totalPrice) => {
            try {
              let monthPay = ((totalPrice * rate) + totalPrice) / numPayments
            }
            catch (error) {
              alert(error.message)
            }
          };
          

Catch block with custom message

          catch(error) {
            alert("Loan rate not calculated. Check the calcPayments function")
          };

          //catch block with no error (available as of ES2019)
          catch {
             alert("calcPayments has thrown error")
          };
          

Create error object / Throw statement

          new Error(message)
          throw errorObj;

          //example 
          const calcPayments = (numPayments, rate, totalPrice) => {
            if(isNaN(numPayments) || isNaN(rate) || isNaN(totalPrice)) {
              throw new Error ("calcPayments incorrect, check loan numbers")
            }
            return ((totalPrice * rate) + totalPrice) / numPayments
          };
          

Finally statement

          //finally will execute regardless if try or catch is thrown 
          try {
            $("some_value").text = sendToFunction(parameters);
          }
          catch(error) {
            alert("parameters not accepted");
          }
          finally {
            $("parameters").focus()
          }