Question

How to use try - catch - finally in JavaScript

Answer 1

try 
{
    my_alert("hello");
}
catch(err) 
{
    document.write(err.message);
}

/*
run:

my_alert is not defined 

*/

 

70+ SQL courses for beginners and professionals

Answer 2

var x = 12
var y = 0
var z;

try 
{
    if (y != 0) 
        z = x / y;
    else
        throw "Division by zero";
}
catch(err) 
{
    document.write(err);
}

/*
run:

Division by zero  

*/

 

70+ SQL courses for beginners and professionals

Answer 3

var x = 12
var y = "zero"
var z;

try 
{
    if (isNaN(y)) 
        throw "y is not a number";
    else 
        z = x / y;
}
catch(err) 
{
    document.write(err);
}

/*
run:

y is not a number  

*/

 

70+ SQL courses for beginners and professionals

Answer 4

var x = 12
var y = -10
var z;

try 
{
    if (y == 0) 
       throw "Division by zero <br />";
    else if (y < 0)
             throw "y is < 0 <br />";
         else 
             z = x / y;
}
catch(err) 
{
    document.write(err);
}
finally 
{
    document.write("finally - do something you must do at the end of this block of code <br />");
}

/*
run:

y is < 0
finally - do something you must do at the end of this block of code  

*/

 

70+ SQL courses for beginners and professionals