NaN error when subtracting

@js_newbieMar 11.2004

I am trying to develop a simple script that will return the age of a certain person by subtraction their birth year from the current year, but i get a NaN error every time i run the script. My code is below:

var id
var bYear = new Array( 1989, 1991, 1995, 2000 );
var now = new Date();
var ynow = now.getYear();
var age = ynow – bYear[id];
id = prompt( “Find age of…”, “Enter ID No. Here” );
alert( age );

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JavaScript

@jaegernautMar 11.2004 — #If I remember correctly the getYear() function only returns a 2 digit year vs. a 4 digit year. For the 4 digit year use getFullYear().

You also may be running into a problem in that you are using the variable "id" before your prompt is setting the value of it.

See if that works for you.

@js_newbieauthorMar 11.2004 — #i tried that, but it still didn't help. im still getting "NaN' when i view the variabe 'age'. here is my exact source code, copied directly from the app.

var id

var fBadge = new Array( "John", "Jane", "John", "Jane", "John", "Jane", "John" );

var lBadge = new Array( "Doe", "Doe", "Smith", "Smith", "Armstrong", "Armstrong", "MacDougal" );

var bYear = new Array( 1900, 1901, 1902, 1989, 1991, 1995, 2000 );

var bMonth = new Array( 05, 01, 02, 02, 09, 11, 06 )

var bDay = new Array( 14, 16, 21, 28, 06, 12, 06 )

var now = new Date();

var fynow = now.getFullYear();

var age = (fynow - bYear[id]);

var id = prompt( "Find information for...", "Enter ID No. Here" );

var bInfo = bMonth[id] + "." + bDay[id] + "." + bYear[id];

alert( lBadge[id] + "," + fBadge[id] + "nBirth Date: " + bInfo + "nAge: " + age );

@jaegernautMar 11.2004 — #You are still using the "id" variable before putting a value to it.

Switch these two lines:

var age = (fynow - bYear[id]);

var id = prompt( "Find information for...", "Enter ID No. Here" );

So they look like this:

var id = prompt( "Find information for...", "Enter ID No. Here" );

var age = (fynow - bYear[id]);

The logic being that you declared the variable but didn't set a value, so when you hit the age = (fynow - bYear[id]); line the id variable just has whatever garbage is in there when you declared it without a value.

So, by flipping the order, you set the id variable from the prompt and the next line will now have a good value to use as the array index.

@js_newbieauthorMar 11.2004 — #hey, it works! ?

thanks a million

@jaegernautMar 11.2004 — #Anytime. Happy to help.

NaN error when subtracting

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