Exception/Error Handling/Holding/Catching - with in the program


Syntax errors: raises due violation of language rules while typing the code.
               -correct/modify the code the according to the language rule.
               -how to identify? 
               - compiler/interpreter

Runtime error: raises while executing the program. 
               when a runtime a error occurs at one line of the program
               program terminates immediately with out executing the rest of the
               lines. this is called productivity loss.

                -due to non availability of resources either fully or partially.
                 resources are files, memory, hardware devices, other softwares,
                 other services etc. 
                -due to wrong or invalid input of the data 
                  -invalid - size, type, format
                           - violation of client business rules

Logical errors: mismatch between the expected output and actual output.
                - verify the steps taken to solve the problem, and correct them.

Controllable errors: no impact on the program , able to avoid the abnormal termination of the program.
Uncontrollable errors: 
                         -hardware/harddisk crash
                         -power

Pre-Defined errors : according to language.
User-Defined errors : according to client.

x
console.log('x : ' + x);
ReferenceError: x is not defined
----------------------------------
var d = Array(-9);
console.log('size of d : ' + d.length);
RangeError: Invalid array length
----------------------------------
var CustomerName = 'John Miller";
console.log(CustomerName);
SyntaxError: Invalid or unexpected token
----------------------------------------

var x = 10;
var y = 2;
var z = 0;
console.log("x : " + x + " y : " + y + " z : " + z);
z = x/y;
console.log("x : " + x + " y : " + y + " z : " + z);
-------------------------
observe the output:
var x = 10;
var y = 0;
var z = 0;
console.log("x : " + x + " y : " + y + " z : " + z);
z = x/y;
console.log("x : " + x + " y : " + y + " z : " + z);
x : 10 y : 0 z : 0
x : 10 y : 0 z : Infinity
---------------------------
console.log('start of the program : ');
for(i=1;i<=5;i++)
{
    console.log('i ' + i);
}
for(j=9001;j<=9005;j++)
{
    console.log('j ' + j);
}
console.log('end of the program');
---------------------------------
console.log('start of the program : ');
for(i=1;i<=5;i++)
{
    console.log('i ' + i);
}
var m = Array(-9); // termination due to error - without executing the code after the array line
console.log('code after the array statement : ');
for(j=9001;j<=9005;j++)
{
    console.log('j ' + j);
}
console.log('end of the program');
output:
------
i 1
i 2
i 3
i 4
i 5
C:\Users\malli\OneDrive\Desktop\JSApp\index.js:6
var m = Array(-9);
        ^
        ^
RangeError: Invalid array length
-----------------------------------
Note: as there is no any mechanism/code to catch the  runtime error inside the program , 
program terminates abnormally without executing the rest of the code after the error occurred line.

try
catch
throw
finally
Error
-------------------------------------------
console.log('start of the program : ');
for(i=1;i<=5;i++)
{
    console.log('i ' + i);
}
try
{
    var m = Array(-9); // termination due to error - without executing the code after the array line
}
catch
{
    
}
console.log('code after the array statement : ');
for(j=9001;j<=9005;j++)
{
    console.log('j ' + j);
}
console.log('end of the program');
----------------------------------------
case2:
------
console.log('start of the program : ');
for(i=1;i<=5;i++)
{
    console.log('i ' + i);
}
try
{
    var m = Array(-9); 
    // here an error object is created with error information
    // that created object is throwned from here implicitly
}
catch(e)
{
    console.log(e.message);
}
console.log('code after the array statement : ');
for(j=9001;j<=9005;j++)
{
    console.log('j ' + j);
}
console.log('end of the program');
---------------------------------
start of the program : 
i 1
i 2
i 3
i 4
i 5
Invalid array length
code after the array statement : 
j 9001
j 9002
j 9003
j 9004
j 9005
end of the program
-----------------------------------
Note: throw - 
var x = 10;
var y = 0;
var z = 0;
console.log("x : " + x + " y : " + y + " z : " + z);
try
{
    if(y==0) // any 
    {
        // error as a string
        // error as a object
        throw 'y value should not be zero'; // any
    }
    z = x/y;
}
catch(errmsg)
{
    console.log('using throw : ');
    console.log(errmsg);
}
console.log("x : " + x + " y : " + y + " z : " + z);

--------------------------------------------------------
var x = 10;
var y = 0;
var z = 0;
console.log("x : " + x + " y : " + y + " z : " + z);
try
{
    if(y==0) // any 
    {
        // error as a string
        // throw 'y value should not be zero'; // any
        // error as a object
        var errobj = Error('y value should not be zero');
        throw errobj;
       
    }
    z = x/y;
}
catch(obj) // obj = errobj
{
    console.log('using throw - Error : ');
    console.log(errobj.message);
}
console.log("x : " + x + " y : " + y + " z : " + z);
------------------------------------------------------------
var x = 10;
var y = 0;
var z = 0;
console.log("x : " + x + " y : " + y + " z : " + z);
try
{
    if(y==0) // any 
    {
        // error as a string
        // throw 'y value should not be zero'; // any
        // error as a object
        throw Error('y value should not be zero');
        
       
    }
    z = x/y;
}
catch(obj) // obj = errobj
{
    console.log('using throw - Error : ');
    console.log(obj.message);
}
console.log("x : " + x + " y : " + y + " z : " + z);
----------------------------------------------------------
Note: raise/birth/origin of error is at one place 
      handling of error is at some other place

function Divide(a,b)
{
    if(b==0) // any 
    {
        // error as a string
        // throw 'y value should not be zero'; // any
        // error as a object
        // origin of error is here - but handled somewhere
        throw Error('b value should not be zero');
        
       
    }
    return a/b;
}

var x = 10;
//var y = 2;
var y = 0;
var z = 0;
console.log("x : " + x + " y : " + y + " z : " + z);
try
{
    z = Divide(x,y);
}
catch(obj) // obj = errobj
{
    console.log('using throw - Error : ');
    console.log(obj.message);
}
console.log("x : " + x + " y : " + y + " z : " + z);
-------------------------------------------------------------------
const Discount = 45;
console.log(Discount);
Discount = 50;
console.log(Discount);
TypeError: Assignment to constant variable.
-------------------------------------------
var Mrp = 256;
var Discount = 19;
var SalePrice = Mrp - Discount;
console.log(SalePrice);
--------------------------------
var Mrp = '256';
var Discount = 19;
var SalePrice = Mrp - Discount;
// string Mrp converted to number then 
// proceeds for any arithmetic operation
console.log(SalePrice);
------------------------------------
var Mrp = 'Arjun';
var Discount = 19;
var SalePrice = Mrp - Discount;
// string Mrp converted to number then 
// proceeds for any arithmetic operation
// But here conversion failed
console.log(SalePrice);
output : NaN
------------------------------
var Price = '69';
var Tax = 19;
// in case of '+'  string + anything becomes string
var SalePrice = Price + Tax;

console.log(SalePrice);
--------------------------------
var Price = '69';
var Tax = 19;
// in case of '+'  string + anything becomes string
//A string to convert into a number.
//Converts a string to an integer.
var SalePrice =parseInt(Price) + Tax;
console.log(SalePrice);
-------------------------------
Note: check the output
----------------------
var Price = '69.29';
var Tax = 19.59;
// in case of '+'  string + anything becomes string
//Converts a string to a floating-point number.
var SalePrice =parseFloat(Price) + Tax;
console.log(SalePrice);
Output: 88.88000000000001
----------------------------------
Note: check the output
----------------------
var Price = '69.29';
var Tax = 19.59;
// in case of '+'  string + anything becomes string
//Converts a string to a floating-point number.
var SalePrice =parseInt(Price) + Tax;
console.log(SalePrice);
Output : 88.59
------------------------