JS Luhn Mass Validate Specific # Of Cards

<script> function luhnCheckDigit(number){ var validChars="0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ_"; number = number.toUpperCase().trim(); var sum=0; for(var i=0;i<number.length;i++){ var ch=number.charAt(number.length-i-1); if(validChars.indexOf(ch)<0){ alert("Invalid Chars Found!!"); return false; } var digit=ch.charCodeAt(0)-48; var weight; if(i%2==0){ weight=(2*digit)-parseInt(digit/5)*9; }else{ weight=digit; } sum+=weight; } sum=Math.abs(sum)+10; var digit=(10 -(sum%10))%10; return digit; } var amm=prompt("Enter Ammount:"); while(amm!=0){ amm--; var inn=Math.floor(Math.random()*9999999999999999); var inn=prompt("Enter Any Credit Card #:"); var out=luhnCheckDigit(""+inn); if(out==0){ var outs=(inn)+"<br>"+outs; alert("Valid Credit Card #!!","","Valid Number!!"); }else{ alert(inn); alert("Invalid Credit Card #!!","","Invalid Number!!"); } } if(outs!=undefined){ var clean=outs.replace("undefined",""); document.write(clean); } </script>