[Nazir]

The alart function is a very useful means of analyzing errors. You can use it at any point in a script to probe objects and variables to see if they contain the data you expect. For example, if you have a function that has several conditional branches, you can add an alert within each condition to find out which is being executed:

function checkAge(years)
{
if (years < 13)
{
alert ('less then 13');
ther scripting
}
else if (years >= 13 && years <= 21)
{
alert ('13 to 21');
ther scripting
}
else
{
alert ('older');
ther scripting
}
}

Maybe the value for years is not coming back as a number, like it should. You could add to the start of your script an alert that tests the variable to see what type it is:

function checkAge(years)
{
alert(typeof years);
:
:
}

In theory, you can put any amount of information in an alert dialog, although a very long string of data could create such a wide dialog that some of the information would be clipped or outside the window. You can avoid this by formatting the output with the escape characters, such as \n for a break line.

[ScottHughes]

Thanks for this information. It helps to add these alerts, because that will save time in the long run when there's an error.