How to loop through HTML Forms collection and validate control values

I have often wondered how to validate form controls that were dynamically generated from a server-side script. Here's my solution in JavaScript:

for (j=0; j<document.theform.elements.length; j++)
if ( document.theForm.elements[j].type == "text" )
{
//Perform validation when the control's type is text
}

if ( document.theForm.elements[j].type == "checkbox" )
{
//Perform validation when the control's type is checkbox
}

if ( isNaN (document.theForm.elements[j].value) )
{
//Perform validation if the control's value property does not evaluate to a number
}

if ( Number (document.theForm.elements[j].value) < 0 )
{
//Perform validation if the control's value property evaluates to a number less than 0
}
}

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