calc-upc-check-digit-bad.js

function CalcCheckDigit(strMsg){
	// calculate the check digit - note UPCE and UPCA check digits are the same
	var Check = 0;            // initialize the check digit value
	for(var X = 1; X <= 11; X++){
      	var Test = strMsg.substr(X-1, 1);
	      if (isOdd(X)==true){
 		     	Check = Check + parseInt(Test) * 7;       // odd position digits multiplied by 7
		}
      	else{ 
            	Check = Check + parseInt(Test)  * 9;       // even position digits multiplied by 9
      	}
	}
	Check = (Check % 10) + 48;  	// convert value to ASCII character value;
	return charFromCharCode (Check);    // check character
}

function charFromCharCode (charCode) { 
	return unescape('%' + charCode.toString(16)); 
} 

function isEven(y) { 
	return (y%2)?false:true; 
} 
function isOdd(y) { 
	return !isEven(y); 
}