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NaN error on subtraction of selectedIndex

Why would the below code return NaN:

alert("DOES NOT WORK - RETURNS NaN:"+document.pollform.month[document.pollform.month.selectedIndex].value - 1);

if I remove the subtraction it works fine???

alert("WORKS:"+document.pollform.month[document.pollform.month.selectedIndex].value - 1);

ASKER CERTIFIED SOLUTION

Roonaan

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ASKER

This is what is actually failing:

age.setMonth(document.pollform.month[document.pollform.month.selectedIndex].value-1);

Zvonko

Check this:

alert("WORKS:"+(document.pollform.month.value-1))

One question for explanation: does JavaScript evaluate the statement expression from left to right or right to left?
And if it is from left to right, what number should yield this: ""DOES NOT WORK - RETURNS NaN: 9"-1;

vikrant4u2

try using the way roonaan has suggested.

i think alert tries to evaluate the msg passed to it.

Zvonko

Your var age is NOT an Object of type: Date

ASKER

It is I just didn't post the whole code!

var age = new Date();

SOLUTION

Zvonko

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